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MIDI

Tony Mills on digital sequencers


Music Percussion Computer and Sinclair ZX81 - the start of something big


Last month we looked briefly at what the US Air Force would no doubt refer to as sequencers of the first and second kinds - simple analogue and more complex digital designs. The ultimate stand-alone sequencers at the moment (providing you read this issue as soon as you buy it and not the week after) are polyphonic MIDI sequencers, such as Roland's MSQ100 and MSQ700. Both these machines can play polyphonic patterns on several MIDI synthesizers, each synth only responding to note information transmitted along the particular one of the 16 available MIDI channels which it's been set to look at.

However, there are such things as sequencers of the third kind, and the word digital gives a clue as to what they may be. What do we know of that's digital and has been around for a good few years now? No, not wristwatches (although a few of those play a nifty reveille if called upon to do so), but computers. MIDI instruments speak to each other in digital codes, and so do computers; it's not difficult to write a language that they can both understand. In fact MIDI was partly designed with home computers in mind, because they have an important and expensive asset - memory capacity. Every not you want to store in a sequencer costs memory space and money, so why waste a large chunk of memory that's already lying about in the form of your home computer?

The first instrument to exploit this useful strategem was the Music Percussion Computer from MPC, which used a Sinclair ZX81 to store large number of drum patterns rather than using costly on-board memory and control inputs. When Uncle Clive Sinclair can turn out cheap units by selling a million computers at a time, there's no point killing yourself to develop a reliable memory and keypad system for your latest musical marvel. Send your customers to their local department store to buy one for £49.95 instead.

Most of the popular home computers now have interfaces available which allow them to address MIDI instruments using various software packages. Many of these packages are sequencers of one sort or another, and since it's much easier to write new software than to discontinue a dedicated sequencer and design a new one, there's bound to be a package which suits your needs more closely than a catch-all like the CSQ or MSQ model sequencers. Examples include the SIEL and RMS interfaces for the Sinclair Spectrum and Commodore 64, the EMR interfaces for the BBC and more recently for the Spectrum and Commodore 64, the Sequential Circuits Model 64 interface for the Commodore, the XRI interface for the Spectrum and various interfaces including the Passport and Roland MPU401 models for the Apple and larger computers.

So what can you do with a computer as a sequencer? This all depends on what software package you've loaded, but different packages on the market at the moment offer simple real-time polyphonic sequencing; 'Live Sequencing' for long patterns without looping; Arpeggiating in various degrees and directions; numerical step time sequencing for up to six monophonic lines; real time polyphonic sequencing with loops, transposition and patch number changing for up to six synths operating on different MIDI channels; '12-Channel Studio' operation with merging, looping and transposition of polyphonic lines; and much more.

Other packages will allow you to produce a graphical display of DX7 parameters for editing purposes, split a 'Master Keyboard' at up to six points to control seven other keyboards playing different patches; add parameter displays to machines without a set of control knobs such as the SCI Six-Traks and the SIEL Expander, and much more. This is where computers have an advantage over conventional sequencers - they don't have to stick to one job. A simple change of software lets them perform all sorts of tasks as well as all sorts of sequencing functions.

In addition, computers are already well set up to sore and recall sequences, patches and other information. Every computer in the world has a disc drive, microdrive, or at least a digital data recorder (cassette player to you mate) available for it, and calling up a stored sequencer is dead easy.

Most new synths are now MIDI equipped


Except under some circumstances, and this is where the problems we hinted at last month begin to appear. Suppose you digitally record a sequencer onto cassette and load it into your computer before a live performance. After you've played it you may want to call up another sequencer for use later. But loading information off cassette is a dodgy business and can take several attempts, while loading from disc drives is okay unless you're using the notoriously slow Commodore 64 system (otherwise the best all-round music computer to have) in which case the process can still take a good 30 seconds. This is not good enough on stage, and there's worse to come. Computers are very prone to disturbances in their power supplies, which is why the manufacturers mount the power transformers in flimsy boxes at the end of long, unprotected lengths of cable with loose connectors (that's enough sarcasm). One good kick (or in the case of the ZX81 a loud cough within 50 feet) and your computer loses its software — not just your sequences, but the compositional program that allowed you to put them in as well. Reloading a program on stage is no fun, the only hope being the Sequential Circuits Model 64 sequencer interface for the Commodore 64, which has its versatile sequencer program built-in (in firmware) and thus unforgettably stored.

One objection raised to sequencing by computer is that it requires specialist knowledge, but with a well-written software package this doesn't extend beyond knowing how to load the computer - all the rest is made plain for you on the screen displays. Other objections to computers as sequencers apply to other sequencers as well - boring, inhuman, and so on. But in fact many of the polyphonic MIDI sequencing packages about at the moment allow for real time playing with modulation, patch change and velocity information all stored, so you can be as expressive as you like. Mistakes can be edited out afterwards (try doing that on tape!) and notes can be corrected to the nearest beat (or 196th of a beat if you're really fussy).

The final major objection is cost, but that's quickly disposed of when you compare the price of polyphonic MIDI sequencer to that of a basic Spectrum set up - about £200 in the latter case, over three times that in the former. A Commodore 64 sequencer set up, assuming you use a SIEL or Rosetti interface at under £100, a disc drive and a black and white TV instead of a monitor, will come out at around £600, a BBC set up at around £800, a new Apple set up at around at arm and a leg (look for secondhand bargains instead).

So the humble computer can have an important role to play as a sequencing device, often with enough capacity to store many long sequences or even whole songs. Next time we'll be looking at something completely different.



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PA Column

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Software Special


International Musician & Recording World - Copyright: Cover Publications Ltd, Northern & Shell Ltd.

 

International Musician - Feb 1985

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Feature by Tony Mills

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