THE LINK BETWEEN the technology of the past and that of the present: little boxes that convert modern MIDI to good ol' 1V/octave Control Voltage and Gate signals. The particular interface under the microscope today is a small grey box called the Cision MCV20.

The MCV20 is a microprocessor-controlled, single-channel, MIDI-to-CV converter with an integral VCA. It runs on a 9 volt supply from a mains adaptor (supplied) and has a non-volatile memory for power-down retention of its working configuration. The converter will operate on any MIDI channel (1-16) and Omni mode, and has nine operating modes to cater for various triggering, gating and velocity options. The front panel has four push-buttons for selection of MIDI channel, operating mode and tuning, and LEDs to indicate power on, MIDI activity and for setting up the unit. On the rear panel there are MIDI In and Thru, and four jack sockets for CV and Gate outs, and audio in and out for the VCA.

Setting up is a straightforward matter of plugging in the AC adaptor (there is no mains on/off switch), a MIDI lead from controller keyboard MIDI Out to MCV20 MIDI In, and jack-to-jack leads (or jack-to-whatever, depending on the synth you're controlling) for CV and Gate control. If you want to use the VCA, the synth's audio path must be diverted through the MCV20 using the remaining jack sockets.

MIDI channel setting is as simple as holding in the Set button on the MCV and pressing the MIDI Channel button as many times as the channel you wish to select - that's up to 16 times for exclusive working and 17 times to get into Omni mode.

Now all you have to do is configure the MCV20 to "talk" to your pre-MIDI synth. Of the nine available operating modes, mode one is a patch enable mode only. The remainder are divided into four VCA, or Velocity, modes and four non-Velocity modes. Two of each of these are single-trigger modes and two are multiple-trigger modes, and for each trigger type there are positive and negative gate options. It sounds complicated but it ensures that all the pre-MIDI triggering options are catered for.

Once MIDI channel and operation mode have been set they can be checked by pressing the appropriate button, which causes the Set LED to flash to indicate channel or mode number. This repeated pressing of buttons and flashing of LEDs is a feature of the MCVs operation. It's laborious but effective and since the operating mode needs to be set once for any particular synth, only the MIDI channel is likely to need resetting during regular use.

The tuning facility on the MCV20 allows the slave synth to be tuned to the controller keyboard. It also allows the slave synth to be pitch transposed over two octaves sharp or flat in semitone steps.

On to the VCA. Where other MIDI/CV converters have chosen to convert MIDI key velocity into a second control voltage, the MCV20 uses it to control an integral voltage controlled amplifier. This allows you to impose a "volume performance" on your old analogue instrument. Obviously this represents a considerable improvement over an old synth's original spec, but it doesn't have the flexibility of other units where this velocity-dependent control voltage may be used to control any parameter the slave synth allows you access to. The most obvious application of this "wild card" controller is to control the filter cutoff frequency - a facility useful in music as diverse as ambient soundscapes and acid house. Shame the MCV20 doesn't have it.

In use the MCV20 performs well and covers all the triggering options you're likely to encounter in old synths - including Moog's S-trigger. The only situation in which it didn't perform properly for me was as a slave to the OSCar's sequencer, when it left me with a droning note. Given the ancestry of the OSCar and the fact that I couldn't reproduce the problem with any other controller, I'm happier to attribute it to a quirk of the OSCar's MIDI spec.

I suppose it would have been nice to be able to tuck the unit away in a rack with a pile of outboard equipment instead of having to find a few square inches of horizontal workspace to support it - especially as it's too light to prevent the weight of leads hanging out of the back to drag it to the floor - but this would undoubtedly have added to the cost of the unit. As there are already more capable and more expensive MIDI/CV interfaces available, the MCV20 is best suited to the budget setup and this shortcoming is unlikely to deter any potential purchaser. It certainly wouldn't deter me.

Price £97.50 including power supply, p&p and VAT.

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