Yamaha's RX-15 Digital Rhythm Programmer (RRP £449 inc. is one of the fastest-selling rhythm machines ever. Julian Colbeck (who's been using it in the studio for several weeks) gives it a 'Long-Term Test'...

I'll be honest, and tell you that I have already reviewed the Yamaha RX-15 for another paper (Shock! Horror!) - but in the intervening time since my initial thoughts were published, I've gone through all sorts of re-thinks and reappraisals of this machine. By some tortuous processes I've now come back to the opinion I first held - but I can tell you, it's been tricky! At one point, for instance, I thought the instrument was bordering on awful - then I realised that it was really me who was obviously bordering on sub-normal (would we comment? - Ed.). Whatever else, it's highlighted the problems of reviewing equipment in any space of time under about two months!

Much of my confusion can be laid at Yamaha's door; or at least, at the door of the guy who wrote the manual. I found that if I read it over and over again I did finally understand what I was supposed to be doing, but not before! Please, Yamaha, any chance of a rewrite???

Anyway, on to the basic facts. The RX-15 uses PCM digitally recorded drum and percussion sounds. There are 13 different sounds, 11 of which have their own instrument button; Cowbell and Shaker you'll find cosily tucked up together (though only for programming - you can have a pattern that finally emerges with both instruments). The available sounds consist of bass drum, snare drum (with an internally varied hi/lo pitch), rim shot, three tom-toms, closed hi-hat (plus internally varied 'stick-hit' closed or 'foot' closed sound), open hi-hat, ride and crash cymbals, handclap, and shaker/cowbell. The snare sound you're unlikely to better, and a cohort/friend who's just bought a Simmons SDS-7 spent many hours not getting close to it. The toms are fine - punchy, and blessed with a pleasing note level; the bass drum is a suitably 'middle of the chest' affair, and in fact only the hi-hats gave me any cause to complain, as they're just a bit thick and heavy. But since each sound's volume is totally in your hands, this problem can be solved by simply turning their level down. Not an ideal answer, but an answer nonetheless. The RX-15's overall memory capacity is 1500 events, which break down into ten songs, made up from any or all of the 100 patterns that can be programmed (a pattern can be any length of bars from 1-99). If this space isn't enough, you can dump data on to tape - but in practice, with careful use of repeats, close examination of patterns etc., you'll find there's plenty of internal room for manoeuvre.

Accents can be programmed too, and the accent volume is variable on all voices. Programming patterns can be in either real or step time, and neither is too taxing on the brain. Above the instrument keys are two rows of oblong command buttons, and above these a small LCD screen. To write a pattern in real time, select pattern mode, find a free pattern number (or 'clear' one if necessary), and press the real time write key. You'll then be confronted by a series of numbers that correspond to the timing value of your pattern, and (on second press) how many bars you wish to use. Default is a standard 4/4 time signature, with the cursor resting alongside the first (number of beats in a bar) figure. Change at your will. Similarly, the length of each beat (second figure) can be changed - the RX-15 is quite happy to play in 13/12 if you can! Finally, the third figure controls the number of bars in a pattern.

If, at any time when initially programming or overdubbing, you don't want to change these figures, simply step through the procedure, continually pressing the real time write button, and you're ready to write a drum pattern. Press 'start', and you're off. A metronome beats away with guide pulses that can be varied from a quarter-note to a 32nd note. The first beat of the pattern is always accented.

There is a certain amount of skill to programming patterns, and as often as not problems can occur if the right quantize level hasn't been set. This can range from a quarter note to a 48th note. Ideally, it's best to get your simpler patterns down with a lower quantize rate, and then increase the rate for fast fills and the more complicated stuff when you're overdubbing. During playback, you are free to to vary each instrument's volume and its position in a stereo image. Unfortunately, there are no individual 'outs' for each instrument.

Step time writing follows much the same setting up procedure, except that the beat moves on (in the smallest measure you've programmed) each time you press an instrument key (or 'yes' key if nothing is intended to be playing at that time). As in real time mode, the pattern will repeat once it reaches the end, and I found a good trick is to keep pressing the 'yes' button in rhythm once you have a basic pattern. That way, overdubs can be slotted in without the need to figure out exactly which beat of the bar a sound falls on. Thus patterns can then be turned into songs, using repeats if you like, to save memory space. However, it's worth noting that you can't simply slot in endless repeat commands all over the place. Once you've programmed a repeat section - say, two verses and chorus - you can't then have a middle section and programme a succession of repeating choruses to finish with.

Being a MIDI instrument, the RX-15 prides itself on being compatible with some of the most unlikely equipment. Yamaha's KX-5 remote keyboard, for instance, can be used to trigger the drum sound, and makes the sounds touch-responsive as well. What a great live concept! Sadly though, although you can play this set-up - assigning each voice on the RX-15 to any specific key on the KX-5 - you can't programme patterns. Ah, well. Now that I've had a fair bit more time and experience with the Yamaha RX-15, I've come to the conclusion that it's a wide-ranging and excellent-sounding rhythm unit - and I freely admit that I'm now a confirmed RX-15 fan. Just as well I wasn't asked to write this review three weeks ago - and don't say - (you were! - Ed.) you were, Ed...

More info, from Yamaha-Kemble Music Ltd., (Contact Details).