In previous Niches, we have devoted a fair bit of space to reviewing software and hardware that help you and your Spectrum create sound and music. Now it’s time we took a look at how your trusty computer can control dedicated music synthesisers. We’ve prevailed upon JON BATES to plug in his musical intellect, and prepare an intro to the world of MIDI. Next issue, Mr Bates willing, we should bring you details of specific devices and name a few synthesiser names for you to try them on...

If you’ve been casting your eyes or ears over music shops or magazines during the past few years, you cannot have failed to notice that more and more instruments and effects are boasting a MIDI INTERFACE capability. Sales pitches aside, a lot of folks aren’t really sure what all this new-tangled MIDI capability is all about. If you fancy yourself as a budding composer of electronic music, and want some help from your Spectrum, read on.

MIDI stands for Musical Instrument Digital Interface, and came into being in 1982 after a high-level meeting between most of the major synth manufacturers in the world. Prior to this meeting of Musical Big Cheeses, manufacturers were plodding on with their own specific ways and means of getting synths connected up and talking to one another. As a result of the variety of ways of going about this, sales were not too healthy and mutual strangulation was imminent.

Most synthesisers were (and are) using digital methods to create and store sounds; it seemed reasonable to come up with a standard which permits synths from different manufacturers to be connected together, thereby doubling the sound. Seems simple, but the story doesn’t end there.

Drum machines have always been capable of sending clock pulses to whatever synth will accept them. This means that the drum machine can effectively control the speed, and synchronise with a pattern of notes put into its companion synth’s memory. Presto. Instant electro-pop with no mistakes (in theory!). Take this one step further, with MIDI, and you can link together a host of synthesisers, all merrily playing one another and presenting a united musical front — all in time with each other. MIDI is much more than a straightforward connecting cable, however.

If one synth can play another — then why not harness the power of a computer, get it to store all the information, and train it to act as Master Conductor. Enter the Spectrum. With a suitable MIDI interface and software, it is possible to fill your Spectrum with a fair number of notes. The really cunning part is that you can give the Spectrum every tiny detail about each note — whether it should be loud, soft, short or long. Furthermore, MIDI is capable of passing on more than these details about individual notes — and can also change from one sound in the synths voice memory to another, thus governing what sound a note should be.

Most electronic synthesisers have the ability to memorise at least 20 ‘voices’, and many can remember considerably more The variety of sounds available is almost limitless. However, you can usually only play one voice at a time on a synthesiser. Link your Spectrum up to one synthesiser via MIDI, and you have something quite clever. MIDI can, however, talk to and arrange to control up to sixteen synthesisers in one go (glad you can afford that many — ED). MIDI can control this many instruments by allotting each synthesiser a channel number — probably labelled on the synth as ‘MIDI channel select’, and it then becomes possible to address each synthesiser directly and tell it which notes to play in which voice.

If you’ve written your multi-synthesiser masterpiece correctly, then all the synths hooked into the system will play along and perform your composition under the careful and precise control of your Spectrum. Not all that many people can run to the luxury of sixteen synthesisers but if you’ve got one, and a chum down the road has another and than there’s that one....

Needless to say, the Spectrum is perfectly capable of acting as a master clock so that drum machines can function in perfect synchronisation with the rest of the amassed technological gadgetry at your disposal.

In order to understand further what MIDI is all about, a little musical erudition is required. Those of you well attuned to the mysteries of music should be fairly familiar with the next few bits of information but hang on in there!

Notes may be entered into a Spectrum either by Real Time or Step Time. Real Time means that the computer tucks away into its memory details about each note as you play it on the musical keyboard — the Spectrum acts rather like a tape recorder. It can then play your notes back to you from its memory, bum notes and all. Cunning software may, however, allow you to edit the bad ones out. Step time, on the other hand, is a bit more laborious. The exact details of each note are entered manually, either by combination of synthesiser and Spectrum keyboard, or directly from the computer’s keys. Step has one major advantage: it leads to music which sounds clean and very together — ideal for all electro-type stuff. It also has a great appeal for those of us with a little less than wonderful dexterity at the keyboard. Results are usually displayed on-screen in musical notation, although some software needs some fairly hectic maths to determine the required amount of steps per note. Also sequences can be created and instigated using step time. (A sequence is a set pattern of notes that is usually repeated over and over to form a basic part of the composition — a musical subroutine if you like.) And it is possible, using complex systems, to arrange a song so that certain sections can be repeated as required.

MIDI controlled synthesisers usually perform in polyphonic (Poly) mode. That is, they will play more than one note at a time. (A piano is polyphonic, a kazoo is not.) MIDI allows such synthesisers to be addressed in three ways: Omni — all the synths play exactly the same notes, all together; Poly — the master controller can tell each synth to receive only information on the particular channel it has been set to (1 to 16) and Mono — any voice in the synthesiser’s memory can be called up to play at any given point within the composition. Spectacular sound changes may be achieved in this way.

One extra facility offered with MIDI in combination with your Spectrum is particularly useful if you can only play by ear, and want to produce a score of your real time composition. Print outs of the music written into memory can generally be made using a graphic quality printer.

Synths are fitted with at least two MIDI ports, IN and OUT, so that they can transmit and receive MIDI information. Many of them also have a THRU port, which enables instruments to be chained together so you can achieve those spectacular orchestral effects alluded to previously.

MIDI actually functions on a modified 8-bit system wherein the first bit of information, the flag, simply defines the nature of the information following — either Status or Data. Status tells the synth which part of it is required to work, while Data tells it what to do. For example, the Status could be ‘Sustain’ — the synth would then access its internal sustain department. The data then following tells it how long to hold, or sustain, the note.

At either end of each byte is a start and stop bit, which marks its beginning and end. Provision is also made for individual manufacturers to allow their instruments to communicate only to each other. This is because some synths have features not found on others.

All in all, MIDI is an immensely powerful musical tool, which is, as yet, only in its infancy. Next month, we should be taking a look at specific interfaces, and some synths which you can mate up with your Spectrum. Watch out Depeche Mode, the Synthesiser Sound of Sid Spectrum’s going to be big soon!