104 SECTION THIRTEEN: KEYBOARD CONTROLS

With the advent of the 3620 keyboard, synthesists could have their cake and eat it too! Delayed vibrato could be achieved without sacrificing a VCO, the VCA and an envelope generator. Delayed vibrato is a feature which can be found on almost every modern synthesizer.

The final parameter of the keyboard’s LFO is its waveform. The keyboard LFO offers users three different waveforms, but the sine wave is the one which the LFO uses by default. One may recall from Section 3 that sine waves are most commonly used for the purpose of creating vibrato. If one wants to use a waveform other than the sine wave, either the triangle or square waves can be used. However, these must be patched by hand to an FM input on each VCO. Separate outputs for each of the three waveforms are available in the upper center part of the keyboard is control panel. It is interesting to note that the ARP’s designers also felt that it was important to provide users with a way to add vibrato from an external source, such as an LFO on another synthesizer, or one of the 2600’s own VCOs. Thus, a fourth jack is provided (EXT VIBRATO IN) which allows a control signal to be input. This control signal is added to the keyboard’s CV and will be output to the VCOs in audio mode as vibrato.

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The 3620 has a nice little amenity built in called repeat. Repeat affects the way the keyboard sends out trigger signals. When this three-position switch (see Figure 13- 8) is in the center position, the keyboard will put out a trigger signal when one would normally expect it to (more on this in a moment). When the repeat switch is moved to the upper position, labeled KYBD, the keyboard will send out trigger pulse after trigger pulse as long as a key is being held down. When the switch is set to the lower AUTO setting, the keyboard will send out a stream of trigger pulses regardless of whether a key is being played. Oddly enough, the rate at which the trigger pulses are sent out is dictated by the keyboard’s LFO. This means that when an external signal such as a square wave is input to the EXT VIBRATO IN jack, that signal will dictate the rate at which the keyboard repeats. This is useful for synchronizing the repeat to other signals.

The repeat feature lends itself to creating many special effects, but since the trigger signals are nor- malled to the EGs, one must remember to use the EGs to modulate something. For instance, the EGs could cause the VCA to function as a gate, thus causing a pulsing sound. Alternately, the EGs could change the pitch of the VCOs. Again, there are many possibilities available to the user here.

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The trigger mode switch allows the keyboard to function in what is sometimes referred to as legato

mode. Legato is an Italian musical term which instructs players to play an attack only on the first note

in a series of notes. By moving the TRIGGER MODE switch to SINGLE, the keyboard will only put out a trigger pulse when a key is played and no other keys are being played. For instance, if one plays and holds a C, the keyboard will send out a trigger pulse. If while holding the C, one plays another key, no additional trigger pulse will be sent out. While this is very musically useful, it takes a bit of getting used to. This is particularly useful in creating the sounds one hears in older synthesizer solos. Early synthesizers (including early versions of the 2600’s keyboard) were stuck in single mode, and as such,

Figure 13-8: The trigger mode and repeat switches

great care had to be taken in playing melodic lines to ensure that each note would sound as the per- former intended it to.

When the TRIGGER MODE switch is set to MULTIPLE, the keyboard puts out a trigger pulse every time a key is played, as one would expect. However, the keyboard will still give the highest note being played priority over lower notes. This means that if one note is played, and then another note below it is played even slightly before the first note was released, the keyboard will not put out a separate trigger pulse for the second note as one might like.

This problem can be solved without making any drastic modifications to the keyboard. If the porta- mento circuit is turned on, but the portamento time is set to minimum, no portamento will be heard. However, the keyboard will now put out a trigger pulse every time a key is played. Because most players have been reared on modern keyboards, this is often the most comfortable way to play the ARP keyboard since this most closely resembles the way modern synthesizers respond.

One interesting trick that can be done in multiple mode is to play and hold a key, and then tap lower keys. While the lower keys won’t sound, the keyboard will still put out trigger pulses, which can in turn reopen the filter or VCA. This is a wonderful feature which is available only on a precious few modern synthesizers.

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To this point, little has been said about the actual keys of the keyboard. The ARP keyboard features 49 full-sized keys. They are made of a durable plastic, which generally resists discoloration unless ex- posed to high levels of tobacco smoke. Like the keyboard itself, ARP used several different internal designs. These designs sometimes differ radically from each other, but the important thing to under- stand about the keyboard is the way it works.

As each key is played, a set of very weak springs are pulled across a set of metal bars which then create the trigger, gate and CV signals. These springs are extremely fragile, and if they become bent, the keyboard may not produce gate, trigger and CV signals at the same time, or may not produce them at all. Thus, it is important to exercise some care when playing the keyboard. Although this design seems very fragile, it seems to hold up fairly well over the years. It is very important that nothing is left sitting on top of the keys as the tiny springs inside could become permanently stretched out and lose their shape.