For longer than I care to remember, musicians have dreamt of being able to control a synthesiser from an acoustic instrument (guitar, flute, trumpet, you name it), or from their own voice. So far, however, all attempts at giving musicians remote pitch-tracking facilities have been flawed and/or horribly expensive.

Digisound's new offering — the PK1 Pitch Tracker — is certainly down to earth, costing under £200. But not surprisingly, it lacks the sophistication of more expensive units and is strictly monophonic. Its circuitry, which employs digital conversion techniques, accepts signals over a five-octave range. This range can be extended up or down to track frequencies between 50Hz and 12.8kHz.

The PK1 makes no sound at all as it stands, so you need to connect its CV and gate outputs to an analogue monosynth before you can do anything musically useful. The gate is the standard positive-going type, but Digisound can supply other types (such as trigger) to order.

The next job is to put in a steady tone from some source, at which point you can adjust the Tune control so that the output pitch from your synth is the same as the input pitch. Alternatively, you can set the output to other octaves or intervals, but it pays to begin simply and then expand your horizons gradually.

That's the easy bit over. Now plug in your vocal/contact mic or electric guitar, and adjust the unit's Input Level and Input Range controls for optimum tracking. Finding the correct setting for the Range control can be a bit hit and miss, but the manual is helpful here, as it gives the frequency range of several potential input sources and lists their appropriate range settings.

A switch named Resolve activates a quantisation facility which organises the output into neat semitone steps; an Envelope Level control outputs a voltage proportional to the envelope of the incoming signal; while a Glide knob controls simple portamento. The two latter functions can be connected to external CV sockets on synths that have them, but the effects they produce can usually be accomplished at the synth end as well.

Finally, a welcome LFO modulation section offers adjustable Rate and Depth, with a choice of sine and triangle waveforms.

In use, the first thing that comes to light is that the Digisound system is extremely fussy about which waveforms it'll accept. It mis-tracks in spectacular fashion when fed with anything complex as it locks onto the harmonics.

Using a vocal input, 'ooh' sounds and whistling work fine, but ordinary speech results in another dose of sonic pyrotechnics — unpredictable, uncontrollable, and more at home on a Star Wars soundtrack than a serious music recording.

As for using a guitar, you'll need to set yours to its least trebly tone on the bass pickup before you'll get a tune out of it, and even then, you'll have to play one note at a time very evenly.

Judging by the way the PK1 tracked whistling, I'd guess that a recorder or flute should work fairly well. Yet even on the simplest of inputs, there was always some degree of mistracking. You can, however, minimise this by invoking the Resolve function, so that all the mistakes come out rounded-off to the nearest semitone.

The PK1 is not a machine for musicians who expect pitch-perfect results on every note — and if you think it's going to give you a foolproof guitar synth, forget it. It won't satisfy the latest generation of thoroughly MIDIfied synth players without a CV-to-MIDI interface, though Digisound are developing one of these as I write.

Meanwhile, experimenters will delight in the range of bizarre sounds that can be had simply by plugging the Pitch Tracker into a long-forgotten monosynth, and then crooning into the mic input. Some pervert has even suggested plugging his harmonica into it.

Getting the best out of the Digisound demands perseverance, imagination and the ability to live with a musical result that may not quite be the one you predicted. But it is great fun, a good deal cheaper than its competition, and very easy to switch off when you've had enough.

Price £199 plus VAT, mail order

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