Cheetah Midi Interface

The following article was taken from Popular Computing Weekly- April 1987

Cheetah has lust about cornered the market in cheap musical add-ons for the Spectrum, having clocked up massive sales of its Spectrum and sound sampler and having latterly the MKS Midi keyboard. Now it has gone the whole hog with a Midi interface and accompanying software which will take your micro into the world of professional music composition - and all for just £49.95.

Those not familiar with Midi (Musical Instrument Digital Interface) need only know that it's a universal digital communication language for processor-based musical instruments. Midi allows you to control one, two, l6 or even more musical instruments from your micro, and is now standard on effects units, sequencers, drum machines, and even guitars and wind instruments as well as keyboards, pianos and synthesisers.

Setting up a Midi system needn't be too expensive - the cheapest Mid drum machine, the excellent Roland TR.505, is around £250, and the CasioCZ-1O1 mini synth is available second hand for as little as £190 (Yamahas keyboardless FS-01 is also a powerful Midi synth although you'll need a keyboard such as Cheetah's MK5 to programme for it).

So. once you’ve chosen your Mid instruments, you're ready to connect them up to the in, out and through sockets of the Cheetah interface. This slots into the rear of the Spectrum (48K. 128K and Plus 2 models). Ordinary Hi-Fi Din leads will do the job, although in fact you’re supposed to use special shielded Midi cables, and the software which comes with the interface is designed to offer you an eight-track sequencer - a system which can record individually, and play back simultaneously up to eight different musical parts

Each part can be polyphonic (can contain up to 16 notes simultaneously) and you can synchronise a drum machine with the automatic Midi clock signal, so as you can imagine, some very complex pieces of music can be composed.

There are two ways of entering notes - in ‘real time’, performed live on the synth keyboard and played back note-for-note by the computer, or in ‘step time', where notes are entered from the synth but played back all with equal timing. Step time entry is better for fast, repeated sequences, real time better for expressive melody parts, and it's good to see both offered on such an inexpensive package.

Sequences can be played forwards or backwards, the velocity with which you strike the keys is recorded as is pitch bend and other performance data, a delay up to seven seconds long in 0.ls steps can be set to create echo effects, and you can transpose tracks to different keys and quantise your performances (correct each note to the nearest beat).

Each of the eight tracks stored can have 16 verses, each verse being from one to 64 bars in length. Each track can be assigned to transmit on anyone of the 16 Mid ‘channels’ so it can address different synthesisers quite independently from all the others.

You can transfer the program to microdrive and it opens with a menu offering some 19 options selected with the up and down arrow keys. The first, 'record a verse', brings up a visual metronome, a value in beats per minute and a quantisation value from 1/2 notes to 1/32 triplets, or ‘Off’. This should be made larger if you want your performance to be corrected into a very regular style and made smaller if you want to retain the maximum amount of free expression. Tempo is variable during recording from 40 to 244 BPM and there's a count-in before you start playing.

You can then 'restart' to layer a new performance, 'merge' to add your performance to a piece already in memory, 'append to the end of an existing piece, or 'transpose' up or down to a new key.

'Track and verse to record' defines which section of memory you work on next, and 'adjust verse length' allows you to set the length of the verse in bars. 'Link 2 or copy 1 verse' allows you to create repeated passages very easily, while 'delete a verse' will come in handy when you're running short of memory.

The most interesting section is probably 'define sequence tracks', which lets you program any verse as a backing, looping if required, so a number of sequences up to 64 bars long can be available at any time for a live performance. Verses are lettered A-P and 'track enable' will allow you to turn off any track if you don't want it to play while you're composing.

'Steptime editing' uses a bizarre display approximating a punched pianola roll. A keyboard logo at the bottom shows which of the eleven available octaves you're working in while the up and down arrows select the exact note, the F and B buttons select the bar and the Z and X buttons move a cursor to the exact point in time at which you want the note to occur. Alternatively you can select the 'N(ote)' option to play the note in from the synth keyboard

Time signature can be set anywhere between 4/4 and 9/8 and you can select some quite sophisticated Midi options -deleting patch change, pitch bend or pressure information to save memory, going into 'omni' (all channel) mode and so on. You can also choose not to send program changes and so on, but you can’t send Midi song pointers which are handy when working with some equipment.

Entering a song involves simply typing in a list of letters corresponding to the verses and sections of verses you
want to hear. This isn't a very sophisticated method and involves a lot of memory work on your part. However, it
should be possible to get used to it (particularly if you write down which verse is intended for which pan of your song) so it's quite acceptable.

One brilliant move has been in the choice of synchronisation options. while Midi clocks are easily dealt with, the spare two pins of the Midi through socket are used to accept 24, 48 or 96 pulses per quarter note plus a Start/Stop signal used by older non-Midi drum machines such as the classic Roland TRSO8.

Overall, the Cheetah Midi interface and software seem excellent value for money. The displays used are boring and far from the professional standards of the Hybrid Arts or Steinberg programs for the Atari micros, but they’re very cornprehensible and move from one to the next quite quickly.

Cheetah deserves every success with this. It's doing so well at the moment that it is moving to new premises after April; the old office (1 Willowbrook Science Park, Crickhowell Road, St Mellons, Cardiff, 0222 777377) will remain in use until April30, while the new office comes online on April 21.

The following review was taken from Sinclair User - June 1987

Midi is the much vaunted link for svnthesisers, drum boxes and other musical hitekerv.

If your synth’s got it, you can record. edit, sequence and generally muck around with music as much as you like without needing to go anywhere near a tape recorder. But you do need a computer with Midi.

Normally the Spectrum doesn’t have one but a Spectrum with Cheetahs interface fits the bill precisely.

And the precise bill happens to be £49.95. for which you get a black box, Midi lead, software and instructions. The box fits on the back of your Spectrum, the lead connects the box on your synth, the software loads in from tape and transfers to microdrive and the instructions get read. No surprise there.

On loading, a list of options appears, selectable by cursor keys and the now traditional menu bar. First choice is ‘Record a verse’ which allows you to tinkle away on your Fairlight and have it recorded for prosterity.

The software treats all music as a collection of versus: once you‘ve recorded one, you can add notes to it, edit

existing contents and play it back in a number of ways. You can link verses together to make up songs, or have them repeat at will ad nauseam.

Having recorded a verse or more, you can get the computer to play back what you’ve got so far on your synthesiser while you record another track. If your synth can handle it, you can play this backing on a different voice, so building up a complete piece of music. I used a Casio CZ-101 For this review, capable of four voices at once - and managed some rather fetching orchestrations of familiar and much loved melodies from Philip Glass et al. (Al’s stuff wasn’t so good.)

Great, but what if your timing is, ahem, a little looser than that perfection for which you (as a true musician) constantly strive?

The software is a pretty understanding creature, It will spare no effort in trying to make the notes it receives fit into what it understands about musical timing. Called quatisation, it tightens up your timing to a given note value - use it carefully - given too much license it will turn Syncopation into strict Sousa. But a well judged sprinkling of quantisation can really help those whose quavers are a touch quaint.

The Midi editor I found strange at first (bit like SU, really). Instead of the familiar stave, the editor shows a section of a verse three bars wide and an octave high. Notes in the verse show as Horizontal lines; their position vertically being their pitch. and the length of line being their length in time. You can edit notes by choosing their pitch with the up and down cursor keys, and their start and end with Z and X. Confused yet?

Alter a pitched battle with the editor for about half an hour (more and more like SU ) I began to like the idea, and it soon became a fairly natural way of working. It’s closer to the way Midi treats music than normal musical notation is, and soon becomes less of a barrier to hand-editing chunks of data than trying to work with crotchets and quavers would be. A nice touch is the ability to add notes during the edit from the computer or the synthesiser. It would have been nicer to hear the current contents of the editor screen without having to leave the edit. Maybe next time Cheetah?

Verses belong to tracks. There are eight tracks, each with 16 verses, and they can be assigned to different Midi channels. Depending on your set-up. different synths tend to have different channels. Changing the synth a bit of music plays on is then just a matter of changing channel numbers, and it becomes too simple for words to remix a song.

Getting down to the minor bits of the package now. There’s a metronome that snaps its fingers in the background to keep the band (you) together. There’s a Midi delay, which sends out data alter a wait. Hooking this back into a svnth with a couple of seconds delay can be an interesting way of building up a short sequence. It can also drive you mad and end up sounding like a New Age record (gulp).

If you’ve got a drum machine you can hook it up to the interface. The tempo set on the drum machine will govern the tempo of the interface plays at. Indispensable stuff – if you’ve got a drumbox.

Thats about it for the software. The hardware is hardy enough. During the course of this review I spoke to the designer, Bob Powell, a couple of times while sorting what turned out to be a duff Spectrum (blush), and learned a few things about the design. It’s clever. The circuit itself is just two chips and a smattering of small components. Considering the performance, that’s nice work. It should certainly make for a reliable product.

I think this is the first Midi package for the Spectrum that I’ve seen that is genuinely useful musicwise.

I could niggle about the software (no indication of memory capacity left. inconsistency in the controls) and the instructions (bit brief and dense), but computer musos should wring fine things from the package.

If you’ve got a Midi keyboard then I wouldn’t hesitate too long before bolting this to the back of your Spectrum.