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Getting the Most from... Mono Mode (Part 7)

Article from Music Technology, February 1987

You may have what seems like the perfect combination of MIDI voice module and guitar controller, but without some kind of interface unit, you may not get the best out of them. Rick Davies points you in the right direction.

For years, keyboard players have had the benefit of split keyboards to take advantage of a synthesiser's ability to play more than one sound at a time. We look at how guitar synth players can use MIDI Mode 4 to do the same, and more.

WHETHER THE GUITAR controller you use is of the pitch-to-MIDI variety (such as the Shadow system), or a guitar-like instrument (such as the SynthAxe or Stepp), when it comes to MIDI, all controllers speak the same language. Some just happen to be more conversant than others, that's all.

Still, the quality of sound you derive from your system depends not only on the capabilities of each component in your system, but also on how well you can establish a link between your controller and your synths.

The guitar controller presents new opportunities to get more out of a synthesiser than may be obvious. Although each string has only a 20-odd note range, it generates the same type of MIDI data as a MIDI keyboard. But since a guitar uses six strings to cover its full range of MIDI notes, it can be dealt with as six independent controllers in one. This is where Mode 4 comes in handy.

Patches, presets, programs, voices. Each manufacturer seems to use a different term for the same thing. For simplicity, we'll use the term "program" since it is used in the MIDI spec. With that matter out of the way, let's consider some of the complication involved in assigning different programs to each string of a guitar controller.

First, we'll consider the ideal situation, in which there are plenty of synths to go around (say six), and each one is to be played by an individual string. Later, we'll consider other, more modest setups. Keep in mind that multi-timbral synths can usually be regarded as several synths housed in one package. Fortunately, most guitar controllers allow notes played on each string to be transmitted on different MIDI channels, so we'll work with this capability assumed implemented in whichever guitar controller is being used.

If we were to set each guitar string to its own MIDI channel, then we'd only need to set each synth to the desired MIDI channel, set each synth to Mode 3, and each string would play the corresponding synth. Although the controller is transmitting over several channels, each synth needs only to receive on one channel for the current setup.

All we'd need to do next is select the desired program on each synth, and we could have, for example, three distinct string synth sounds on the first three strings, and brass, clav, and bass guitar sounds on the last three strings.

The advantage of doing things this way is that you can play the same note on different strings and get a different timbre each time, just as you would on a real guitar - though in this case the differences in timbre may be a bit more drastic than they can ever be on an acoustic guitar.

But the above arrangement involves a fair deal of setup time. Now, suppose you need a different synth arrangement for another tune. If you were to repeat the process described above very often, you'd eventually get pretty fed up. So the idea is to use MIDI program-change messages to set up all of the synths simultaneously, under the control of the guitar.

There are a couple of ways of doing this. Obviously, you'll want to change programs on all six synths, but since each synth is set to a different MIDI channel, you'll need to send out six distinct MIDI program-change messages, one over each of the six MIDI channels in use.

The Shadow (or Ovation, or Charvel, or Takamine) GTM6 guitar controller gets you going in the right direction by allowing you to transmit three program-changes in one go, using a "parallel chain" feature which lets you build up three series of program changes which can be stepped through with a footswitch. Since each of the three chains can operate over a different MIDI channel, the GTM6 system will take care of three synths.

So if three synths are enough to keep you busy, you could assign pairs of strings to the same MIDI channel, and the GTM6 could control the program changes from there. For example, the first two strings could be assigned to channel 3, the third and fourth strings to channel 4, and the fifth and sixth strings to channel 5. Although this is a compromise of sorts, it's certainly a step in the right direction.

Not all guitar controllers have such a multi-channel program-change capability, however. For example, if you happen to use the Ibanez MC1, you can send program changes over any one channel at a time, but you'll need external assistance to get the message across to more than one synth.

Fortunately, there are devices designed to do this for you. For example, the JL Cooper MIDI Link has one MIDI input and six MIDI outputs. The MIDI Link connects between the guitar controller and the synths, so the controller can be the origin of all program changes. In fact, since the MIDI Link has six MIDI outputs, you can connect each synth directly to one output, rather than rely on chaining the synths together with their MIDI Thru sockets.

When the MIDI Link receives a program-change message over MIDI, it transmits any combination of MIDI program changes over any combination of MIDI channels, out of any combination of the six MIDI outputs. All you need to do is program your desired program combinations into the MIDI Link, and it'll take care of the channel and program assignments. The MIDI Link does this without affecting any other MIDI messages. And with its six MIDI output ports, it's a machine that's well suited to solve the kind of problems you might come across.

Another American company, Voyce, have a couple of MIDI accessories which can be used to help rearrange several synth programs simultaneously. Their LX4 and LX9 can handle four and nine channels of MIDI data respectively, so you would have to take into consideration how many synths you are going to use before selecting one of these models. In addition to transmitting multiple MIDI program-changes upon receiving one, the Voyce units also handle note transposition and other handy data manipulation.

K-Muse (American again, I'm afraid) have a MIDI foot controller coming out in early 1987 which connects to the Photon guitar-to-MIDI converter's MIDI input. When you select a program on the foot controller, several program-change messages are transmitted over individual MIDI channels. Since this foot controller will also contain other special controls for the Photon, it should be a desirable addition to the system. Still, it won't help other guitar controllers to deal with multiple program-changes. So far we have assumed that each synth requires a distinct program change. But if you're prepared to do a bit of planning, you can arrange your synth programs so that when each synth receives the same program-change message, the desired sounds are selected. For example, program 00 could be a brass patch on one synth, strings on another, bass on yet another synth, and so on. The only thing you'd have to do then is find a way to send program changes over six individual MIDI channels.

An economic solution to this problem is the Alesis MPX MIDI Transmitter, a battery-operated program selector which, thankfully, is available in the UK through Sound Technology. This device normally transmits program changes over only one channel at a time, but thanks to Alesis' decision to include a "Channel 0", a single program selection on the MPX can cause that program change to be transmitted over all 16 channels.

If you choose to use this method, be careful you don't have any other MIDI instruments connected to the MPX which you do not want to respond to program changes. And even though this method works, and it may appear simpler to have all synths playing the same program numbers at all times, arranging your synth programs into the appropriate memory locations requires some planning, and will probably require you to store copies of some programs in several memory locations, which is not terribly efficient.

On the other hand, if you happen to be using an Oberheim Matrix 6R synth module, you'll find a special "patch mapping" facility which enables the synth to change to any program upon receiving a different program number over MIDI, so there's no need to copy programs into other memory locations.

At the top end of the guitar controller market, the SynthAxe takes care of all of your worries. Whether you choose to select a program from the controller or step through a series of program changes, multiple program-changes are transmitted over as many MIDI channels as is required by your system.

We've assumed that we're dealing with synths capable of playing only one sound at a time so far, whereas there are a large number of instruments with keyboard split, layering, or even multi-sampling capabilities.

If you control a split synth from one string, then the split-point becomes a fret on the corresponding string rather than a key, and each string can play as many programs as the corresponding synth has to offer. On the other hand, if you play your cards right, you can use one synth to take the place of several.

Take the example of a synth with a split capability. The Matrix 6R has a handy Mode 4 implementation which allows its left and right programs to be played over separate MIDI channels. Since the left and right programs also have programmable zones (note ranges to which they are assigned), a guitar controller can use the Matrix to cover two strings separately, or more strings if having only two sounds is acceptable.

As you might have noticed by now, there are still some differences to be sorted out between guitar controllers and the synths they drive, even though several manufacturers have MIDI accessories to fill the gaps.

More recent entries into the guitar controller market appear to have corrected some of the limitations of earlier models, which indicates that designers are doing their best to eliminate the need for additional MIDI accessories.

The possibilities are many, and with a bit of planning and patience, a guitar con earn its keep as a master MIDI controller.

Series - "Mono Mode"

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Sequential Studio 440

Publisher: Music Technology - Music Maker Publications (UK), Future Publishing.

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Music Technology - Feb 1987




Mono Mode

Part 1 | Part 2 | Part 3 | Part 4 | Part 5 | Part 6 | Part 7 (Viewing)

Feature by Rick Davies

Previous article in this issue:

> Patchwork

Next article in this issue:

> Sequential Studio 440

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