"GF" Peripheral Devices
Designs, Dimension and Descriptions
1988 © J.Brent

 LPVP Peripherals

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GF Peripheral Devices
Designs, Dimensions and Descriptions

This folio covers the physical dimensions of certain peripherals in the GF line of products, and their relation to GF-representation. Although references are made to these peripherals throughout the text of the GF-representation SOFTWARE PACKAGE DESCRIPTION, we will examine here in detail the: a) Genealogy, b) Philosophy, c) Features, and d) Physical dimensions of each GF-Peripheral.

LPVP Peripherals

 Genealogy:

Remembering that GF-representation represents the Pitch-Duration-Volume characteristics of events over a moving grid of time, the devices here are (with the exception of the monitor screen) designed to alter or control the Pitch (number of oscillations per second - Hz), Duration (the length of time in milliseconds that a given even lasts from start to finish), Volume (relative volume in decibels assigned to the specific colors of the GF-Spectra), and/or placement of the occurrence of the event with regards to the time grid.

a) "RAT"

Genealogy:

In a musical context, the RAT is incapable of functioning without the GF-representation software. The RAT is a special LightPen capable (at its simplest conception) of inputting Pitch and Duration data, and controlling the placement of events on a moving grid of time. Without the invention of GF-representation the invention of the RAT would not have been possible.

Philosophy:

The RAT is designed for use by either right-handed of left-handed people of any hand size (it might be unsuitable for very small children.)

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Features:

The RAT may be said to only possess TWO "moving parts". The first that we'll consider is the LightPen head.

The LightPen head is only capable of effecting changes in Pitch. In real-time it operates in ONE dimension only, ie. it moves either up or down along the "NOW-Line". The computer can then tell the frequency of the event by the LightPen's vertical position on the monitor screen.

The second set of "moving parts" is slightly more involved. This consists of two movable piano-keyboard-like KEYS (they aren't really buttons) which perform identical functions. The KEYS may be depressed by the user. When not being depressed by the user they are sprung back to the released position. When a key is depressed while the LightPen head is on the "NOW-Line", KEY-ON data is sent corresponding to the LightPen's momentaneous vertical position on the "NOW-Line". Duration is normally considered to be for the amount of time that the KEY is depressed. Upon release the "KEY-OFF" message is sent.

These KEYS are also capable of sending MIDI-Velocity data (both Velocity-On and Velocity-Off) and of transmitting AfterTouch data.

MIDI-Velocity data for Velocity-On sends data with regards to how hard (or soft) the KEY is initially struck. Normally, this message affects volume content, but (depending on how the program in the MIDI sound generating device is set up) often affects harmonic content or other parameters as well.

MIDI-Velocity data for Velocity-Off sends data with regards to how abruptly or slowly the key is release.

MIDI-AfterTouch data is information with regards to how deeply the KEY is depressed after it is initially struck. At the moment this is generally used to create MODULATION effects (in classical music notation - hereafter referred to as CMN - these are Vibrato effects or Tremolo effects), in the future AfterTouch could quite conceivably be used for a number of other things. These MODULATION effects (altering Pitch and/or Volume with an LFO generated wave) are more intense if a relatively strong degree of pressure is exerted and the depth of the effect may be varied in real-time by the user at their expressive desire. If the user does not want

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any MODULATION effects it's simply a question of the user exerting so little pressure that the effect goes to zero without actually releasing the key. This depth is the pre-AfterTouch-point. Nowadays every synthesizer on the market has AfterTouch, and this pre-AfterTouch-point has been pretty much standardized as far as the comfortable depth.

We have seen that the RAT can control Duration by means of KEY-ON/OFF messages. Pitch by means of the vertical placement of the LightPen Head on the "NOW-Line", and that other parameters may be effected by means of the Velocity- Sensitivity and AfterTouch-Sensitivity transmitting capabilities of the RAT's KEYS. These parameters may include: volume (both with Tremelo effects from the LFO and Velocity-On/Off), pitch (AfterTouch only - this corresponds to Vibrato), and the harmonic content (this could theoretically be assigned to either AfterTouch of Velocity-Sensitivity, but in general the harmonic content is more likely to be affected by how hard or softly the KEY is struck initially).

Other uses for the RAT include: its substitute for MOUSE functions while not WRITING GF-representation on the monitor screen. Possible functions include: choosing menu items, dragging things around, changing parameter values, ie. the LEFT KEY corresponds to subtraction of increments and all negative functions and the RIGHT KEY corresponds to all positive functions, addition of values, etc, and just basically anything a MOUSE can do.

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 RE: Size of KEYS:

Speed of execution is the reason for having two KEYS with identical functions instead of simply one, and this point has been elaborated on in various places throughout the "GF-representation SOFTWARE PACKAGE DESCRIPTION" and needn't be labored here. It is to be noted that the RAT is intended to be played by the MIDDLE finger (on the LEFT KEY if you're right-handed) and the RING finger (on the Right KEY - if you're right-handed), NOT index-finger/middle-finger. The reasons for this are because of the manner the RAT must be held.

It is true that the RAT's KEYS resemble piano-keyboard keys. The primary reasons for this choice are WIDTH and LENGTH. 

WIDTH-

If two adjacent fingers are to execute alternating keystrokes, the keys must not be too close together nor too far apart. They must not be too narrow for the human finger (or too wide either). Now since the size of human hands vary greatly and even finger thickness, a certain compromise has to be made to everyone's general satisfaction. I'm certain the man that invented keyboards in the first place and the conventions which finally gave rise to a standard width for all keyboard keys (meaning musical keyboards, of course) put a lot of thought, energy and experimentation into this. Why search for a more ideal width? 

LENGTH-

As some people's fingers are thicker or thinner, so are some people's fingers shorter or longer. And the difference between adults and children can vary incredibly. I would like the RAT to be equally playable for a child of 9 or for the largest man's hands. If the length on the model dimensions is not perfect, at least it's a place to start looking for the "perfect compromise".

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Other physical features of the RAT include: 

             The Thumb Pad

             The Palm Pad

             The Velcro Strap 

* The Thumb Pad is mainly for comfort but also adds stability, and a certain amount of shock absorption. Rubber (not too hard) may be chosen for its durability and shock absorbing properties, but may become slippery from sweat. Old rubber also has a tendency to crumble when it gets exposed to heat. Plastic has disadvantages because it doesn't let the skin breathe. Perhaps a material which has the ability to absorb sweat, retain a high coefficient of friction at all times with the human skin, solid yet with the right "give", and easy-to-clean would be ideal. 

* The Palm Pad (in conjunction with the Velcro Strap) provides stability and helps to provide a snug and comfortable way to hold the RAT. 

* The Velcro Strap (in conjunction with the Palm Pad insures that the RAT is securely attached to the hand. The Velcro Strap is, of course, adjustable to all size hands. 

The RAT (GF's LightPen) has been referred to on pages 9, 18, 19, 22, 23, 24, 28, and 120 of the GF-representation SOFTWARE PACKAGE DESCRIPTION and also on page 12 of its accompanying ADDENDA.

pg 9a

pg 10 

Photo of "RAT" prototype model

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Photo of "RAT" prototype model

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b) MIDI Volume Pedal

There must be a continuous controller in the shape of a pedal that is capable of transmitting MIDI Volume data on the market at a reasonable price. Keeping in mind that this new musical instrument's name "LPVP" means "LightPen/Volume Pedal" (LightPen basically controlling Pitch and Duration / Volume Pedal controlling "expressive" volume) the Volume Pedal is clearly indispensable to the instrument. However, this doesn't mean that a Volume Pedal is the "perfect" or only means to send "expressive" Volume data.

There are several drawbacks to using only a pedal to control "expressive" or for that matter even general volume change situations. If, for instance, you're standing up looking at an audience and you set your Volume Pedal to a comfortable volume level somewhere between the 0% and 100% limits of the pedal's "action", and then take your foot off momentarily ... Firstly, there's a good chance the pedal is going to move slightly as you're removing your foot. If the sound suddenly cuts out, or even worse gets louder than it should be, the results in either case can be annoying to both the audience and the player.

There is also a great risk that when puuting the foot back onto the pedal that the pedal will accidentally be moved to an unwanted position before the foot gains total control over the pedal.

Volume Pedals in general don't have a very high "friction" or "tension", and so they are in fact quite easily moved. Too easily for certain uses.

There are two solutions to this problem: 1) always keep your foot on the Volume Pedal. This is just simply not necessary, so why do it? Maybe a sit-down player could do it, but if you're supposed to be dancing while you're playing - forget it. 2) My solution is to set the extreme range of the pedal to a comfortable maximum, this way at least I know that it won't get suddenly louder as I try to delicately put my foot down without moving the pedal.

Still, a volume pedal is very useful and is great for things like organ swells, horn crescendos, fade outs and even Leslie (Tremolo) effects.

To make up for the abovementioned deficiencies, the Volume Pedal and the contiuous Volume Controller on the the "MP" (qv. This folio pg 15) work together in a complementary fashion.

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c) Sustain (or Hold) Pedal

As long as we're on the subject of pedals, let's have a look at the Sustain Pedal. There are plenty of these on the market, too. However the Sustain Pedal for this system requires a pedal capable of not only sending the HOLD message but it must also transmit MIDI Velocity Off information. This works exactly the same way as Velocity Off on a normal synthesizer's keyboard, ie. if the pedal is released abruptly the Volume Envelope is sent straight to zero. And if the pedal is released slowly the slope down to zero volume is less steep depending on what is called the "release time" which of course corresponds to the time it takes the user to completely release the pedal.

The "audio-visual freeze-frame" properties, etc are discussed on pages 7, 9, 18, 22, 26, 41, 116 of the GF-representation SOFTWARE PACKAGE DESCRIPTION.

The Sustain Pedal's main function is to extend the Duration of an event after the key which originally triggered the event has been released. Note also that a Sustain Pedal which transmits MIDI Velocity Off data has a certain degree of control over volume (this only has control over how quickly or slowly the sound decays, ie. once you begin letting off the pedal the sound can only decrease, never increase).

 
d) "MP" (Modulation Peripheral)

References to this peripheral, which is referred to as the "MOD-Wheel Box", are to be found on pages 1, 18, 19, 23, 25, 53, 78, 80, 81, 117, 118, 119, of the GF-representation SOFTWARE PACKAGE DESCRIPTION, and also on pages 12, 13, 14, 15, 16, and 17 of its accompanying ADDENDA.

On the present model of this box, there are two continuous controller wheels, two 8ve (octave) buttons, one joystick, and one sliding potentiometer for data entry. 

(1)   Modulation Wheel Continuous Controller

(2)   Volume Wheel Continuous Controller

(3)   8ve buttons

(4)   Joystick

(5)   DATA ENTRY slider

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(1) Modulation Wheel Continuous Controller

This controller does exactly the same thing as the Modulation Wheel on any synthesizer, ie. it creates modulation effects (pitch modulation = vibrato, volume modulation = tremolo) which are controlled by the frequency and type of wave generated by an LFO (Low Frequency Oscillator). GF-representation (as described in the SOFTWARE PACKAGE DESCRIPTION) is capable of displaying pitches to a degree of approximately +1.98 cents. While this is a resolution high enough to represent a common "comfortable" vibrato, it also means that the RAT is incapable of effecting any changes in pitch smaller than +1.98 cents. In order to create modulation (vibrato) effects smaller than that number a MOD Wheel is needed.

In the case of vibrato (pitch) effects, the further the wheel is pushed (depending, of course, on the internal settings of the sound generator which is being controlled) the larger the variation in pitch will be. This controller sends MIDI modulation wheel data.

Tremolo (volume modulation) effects, if engaged, operate similarly in that the further the wheel is pushed the greater the deviation from the initial volume level.

In some synthesizers these modulation signals can also be used to increase or decrease harmonic content according to the speed and type of low frequency wave issued from the LFO.

(2) Volume Wheel Continuous Controller

Traditionally, the "on-board" volume controller on sythesizers is a sliding potentiometer. I have decided to break from tradition here in order to make the "on-board" controller ultimately more playable.

A sliding potentiometer is designed to set the main volume and leave the expressiveness to the foot pedal. That is to say, a sliding potentiometer is made to be moved to a certain level and to stay there until another major move needs to be major (often synthesizer programs have inherently different volume levels and shortly after a program change it is usually necessary to adjust the "main" volume to a more balanced level), this means that sliding potentiometers

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are not actually designed to be "played". Should the user decide to "play" their "main" volume sliding potentiometer (eg. to create tremolo effects, violent crescendos or decrescendos, etc) sooner or later the sliding potentiometer will begin showing signs of wear. These signs of wear are usually manifested by the appearance of "audio-grit" whenever the slider is moved, or the slider itself becomes wobbly or difficult to move smoothly.

The advantage to a wheel controller is that wheels are made to be played! And wheels actually encourage expressiveness. Of course, the friction (or tension, if you prefer) on the wheel must be quite high in order to avoid drastic volume changes at a slight touch and to insure that the volume level stays where you want it to. That is to say that the "tension" on the Volume Wheel Continuous Controller is much "higher" than the tension on the Modulation Wheel Continuous Controller.

Please note that neither of the two wheel controllers on the "MP" is sprung.

The Volume Wheel Continuous Controller occupies the space where the PitchBend Wheel is traditionally located. (A PitchBend Wheel is normally sprung to return to the middle position and has a range of +50%. Both the Moulation Wheel Continuous Controller and the Volume Wheel Continuous Controller have a range of 0% to 100%).

When controlling Pitch with the RAT (qv. page 119 of the GF-representation SOFTWARE PACKAGE DESCRIPTION) in continuously variable function (as opposed to chromatic semitone function) a PitchBend Wheel is unnecessary because the RAT's LightPen Head can (with a little help from a special Portamento) effect PitchBend changes of any interval.

If the user decides (even with the incredibly sensitive capabilities for changing pitch that the RAT makes possible) that a PitchBend function is necessary then two opposing points of the Joystick (qv.) may be assigned to this function.

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(3) 8ve buttons

As opposed to what I wrote in 1987 with regards to the octave transposing function requiring 4 buttons (page 24 of the GF-representation SOFTWARE PACKAGE DESCRIPTION), only 2 buttons are actually needed.

At program change the overall pitch range is defaulted to its normal position. Pressing the right 8ve button once will raise the overall pitch range one octave.

If commencing from normal position and the left 8ve button is pushed, the overall pitch is lowered on octave.

When writing PDV data (Pitch-Duration-Volume) with the LPVP, the user has only the choices of using an F-noninteractive staff, or a G-noninteractive staff (the RAT is only capable of writing in one track resolutions).

When writing on an F-noninteractive staff, pushing the right 8ve button twice will raise the overall pitch range two octaves, and, when commencing from normal position - pushing the left 8ve button twice lowers the overall pitch range two 8ves.

The 8ve buttons serve additive and subtractive complementary functions, ie. if the overall pitch range has been transferred to two octaves above normal position, pushing the left button once will bring the overall pitch range down to one octave above normal position.

Pressing the left button once again brings it back to normal position.

If we press the left button again, we'll find ourselves and octave lower than normal position, and if pressed once again we'll find ourselves at the lowest range possible in GF-representation, that is: two octaves below normal position.

At this point pushing the right octave button takes us up to a position one octave below normal position, pushing the right 8ve button a second time brings us back to normal position.

Pressing the right 8ve button once again raises the pitch one octave, and finally pressing one last time on the right 8ve button we arrive at the upper range for the F-noninteractive staff - two octaves above normal position.

The only difference here between the treatment of the F-noninteractive staff and the G-noninteractive staff is that the upper limit for the overall pitch range is 4 octaves above normal position (however, the lower transposition limit still remains at two octaves below normal position as in the case of F-noninteractive staff).

pg 17 

The philosophy here is: If you're in G clef there's no need to have the ability to transpose down three octaves - just change to F clef.

Similarly, when writing with the RAT on the F clef there's no point in transposing up three octaves here either because you should use the G clef for operations in that pitch range.

I realize that there are musicians who are only used to reading in one and are loathe to learn anything about the "other" clef, but GF-representation is Music Notation and in the world of REAL music REAL musicians must be capable of reading both clefs.

A capability of 3 octaves above normal position is a must because that brings us up to C8 (8372 Hz) which is the standard high note for synthesizers. This then matches other manufacturers' capabilities and aids in compatibility.

Depending of course on tracking pitch and its difficulties at extremely high frequencies, I would like to add yet another octave, ie. a capability of 4 octaves above normal position.

The reason for this is that Bird Calls (songs) may have a frequency of up to 12kHz, while this is not a full octave above our approximated 8kHz, it's still just high enough that if we decided to document Bird Calls and didn't have this capability then it would have to be built in special.

As far as the lower limit of transposition is concerned (F-noninteractive staff / two octaves below normal position ) the extreme low note (C-1 = 16.35 Hz) is already 9 semi-tones below the standard musical low note (A-1 = 27.5 Hz), so there's absolutely no need to exceed this limit as far as I can see.

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(4) Joystick

The four points of the Joystick (beginning at the top and moving clockwise) are: North, East, South and West. These are referred to as North Point, East Point, South Point and West Point, and abbreviated: N, E, S, W. (Why this simple intuitive designation of Joystick points isn't already the worldwide standard is beyond me. In fact no Joystick I've ever seen uses the compass to designate its four points! Most are designated: 1, 2, 3, 4. For that matter they could have just as confusingly designated them Hearts, Spades, Diamonds, and Clubs).

The Joystick is sprung to return to its center position when released. Any of the four Joystick points may be assigned to any controller function.

An example of a possible use for these user programmable Joystick-point-functions was given in this folio under the section on the Volume Wheel: the user could assign the East Point to positive PitchBend, the West Point to negative PitchBend, and then program the North and South Points to something else (or program them to do nothing, for that matter).

Another possibility would be to assign positive PitchBend to the North Point, negative PitchBend to the South Point, and maybe the East and West Points could control vibrato and tremolo respectively.

There are obviously a great number of things that could be assigned to these points (and undoubtedly there will be more in the future), and an even greater number arising therefrom, so we will only present one more example of the possibilities afforded to the user.

The North Point could be assigned to control Pitch Modulation (vibrato), and the East Point could be assigned to control Volume Modulation (tremolo). In this way, pushing the Joystick in a NorthEasterly fashion would bring in both effects simultaneously and any bias in a North OR East direction would proportionately "mix" the relative depths of the respective vibrato or tremolo effects. Very handy!

The South and West Points could be assigned to open harmonic filters (Wah effect) or Breath Control, or etc,

Joysticks have been around for a long time and their use with musical (computer) instruments and with computers in general is well established, therefore a Joystick is included on the "MP".

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(5) DATA ENTRY Slider

This is a sliding potentiometer used for raising or lowering increments of data quickly over a wide range. Sliding potentiometers for coarse data-entry, while virtually essential to synthesizer programming are, in fact, not included on QWERTY keyboards. The DATA ENTRY can input during Write Mode, Edit Mode, and it can even effect many audio parameters in real-time depending on which parameter is currently in its "window".

Fine data-entry while Editing, etc. can be input increment by increment via the RAT or QWERTY keys.

As the RAT was designed to be played by either right- or left-handed people, the "MP" also had to be "playable" by either the right or left hand.

The "MP" is not set up symmetrically like the RAT so consequently there are slightly different techniques for "playing" this peripheral.

Right-handed people are expected to play the "MP" with their left hand. This means that the thumb controls the Joystick, the octave buttons are taken care of by the index finger, the side of the palm or ring finger or middle palm or finger may control the Volume and MOD Wheels.

For the left-handed person, who would be playing the "MP" with the right hand, the situation is a little different: the Joystick is worked by the palm of the right hand (one could say the right hand palm is "dedicated" to the Joystick), I found this to be quite comfortable, even to feeling it somehow "belonged" there. The Wheels here are controlled by the thumb or ball of the thumb, the 8ve buttons can easily be hit by the ring finger, and in both cases the DATA ENTRY is always accessible.

The philosophy behind the "MP" has always been: All controllers should be "At your fingertips", ie. the controllers must be placed close enough together that you don't necessarily have to stop touching ("playing") one controller in order to change something on another controller.

The fixation methods (the "MP" must be solidly fixed and cannot "wobble" about) may be: 1) Suction Cup. This method only works on glass table tops and I've always found that they still slide around, therefore suction cup fixation is deemed unsuitable for professional situations.

pg 20

Other fixation methods include: table clamps for home use, bar clamps for on-stage use on (keyboard) rack bars, and maybe even Velcro! The point is that the "MP" must be solidly fixed and completely stable under many different circumstances depending on the physical situation it is used in, and therefore has to be easily adaptable to the user's personal set up.

e) monitor screen

Needless to say the monitor screen plays an enormous part of this new musical instrument called LPVP. What happens On-Screen in GF-representation is well described in the SOFTWARE PACKAGE DESCRIPTION (qv.) and the principles of Pitch = height, Duration = length, and Volume = colors (GF™) should be well understood by now, so we'll move on to screen size:

The screen must be no less than 800 monitor lines high. The G staff in one track resolution is 672 monitor lines thick, that leaves 64 lines at the top and bottom free for other uses.

The F staff in one track resolution has 696 monitor lines and only 52 monitor lines each side.

 A runner or chanel made of molded clear plastic traverses the monitor screen vertically at far right. This plastic (or nylon) runner coincides with the placement of the "NOW" Line.

Not only does this aid the RAT's LightPen Head to always be right on the "NOW" Line, it also protects the face of the screen from getting scratched up.

Indented "notches" at the semitone intervals on the inside of one side of the runner (channel) may enhance intonation and add as important landmarks for the player.

The other side of the channel should be smooth for glisses.

pg 24

Photo of "MP" (Modulation Peripheral) prototype model

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Photos of "MP" (Modulation Peripheral) prototype model

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