Each month we review the latest Electro-Music Equipment — from synthesisers to sound reproduction and effects! E&MM's special in-depth reviews look at what's new in the world of commercial music — a vital updating for both electronics designers and musicians.

I have to admit at the outset that I totally approve of any manufacturer who has the courage to develop an interface between human and synthesiser that doesn't involve keyboards, joysticks or modulation wheels. The one quality that's usually missing from keyboards (apart from the acoustic piano) is the ability to really sense an actual mechanical connection between the muscular action that causes your fingers to strike the keys and the sound that is produced so many microseconds later. Velocity-sensitive keyboards go some way towards alleviating the frustration caused by this physical deprivation, but what I really need is touch feedback, or 'feel'. In this respect, the development of synthesisers has been retrogressive, as the first electronic keyboard instrument, the ondes Martenot, invented in 1928 by Maurice Martenot, provides this touch control in a way that no synthesiser manufacturer has ever bothered following-up. An article on this instrument, together with a constructional project for a unique touch control system applicable to any synthesiser, will hopefully appear in a later issue of E&MM. For the time being, though, I'd like to recommend anyone interested in hearing the power of the ondes Martenot's touch control to listen to either, the Chant d'amour section of Messiaen's Turangalila Symphony or the Concerto for ondes Martenot and orchestra by Andre Jolivet.

The Blacet Syn-Bow questions the over-mechanical nature of operating a synthesiser, and returns, though I don't think that Blacet are aware of this, to modes of control used in the 50-year-old ondes Martenot. As you can see from the photographs, the Syn-Bow totally does away with conventional input of pitch. Instead, Blacet use the simple device of a 7¾" plastic rod, or what they call a 'frequency bow', attached to a potentiometer. Since the potentiometer slider travels through an angle of 300° this means that the end of the frequency bow describes ⁵/₆th of a circumference of 48", i.e., 40", which is a lot of resolution from something as simple as a plastic rod and a pot! At the other end of the instrument there's a touch sensor consisting of the sort of piezoceramic device used for 'beeping' and a foam pad to cover it. Pressing down on the sensor pad with one or two fingers of the left hand (see photo for my inimitable playing technique) strains the piezoceramic crystal and produces a voltage output that is proportional to the pressure applied. After buffering, the sensor then provides a control voltage for controlling the various sections of the Syn-Bow. The rest of the Syn-Bow centres around the Texas Instruments SN76477N, the sound generator chip usually dedicated to blasting things out of space and sky rather than such sophisticated activities as making real music. This chip includes three sound generators: a SLFO, VCO and noise generator. However, in the Syn-Bow only the first two are used. The frequency range of the VCO is set to give three octaves over the 40" resolution of the frequency bow. The basic output of the VCO is a square wave, which, as it stands, isn't particularly interesting. Some variations on the basic waveform are introduced by frequency modulation applied to an external VCO control input on the chip, and by using the SLFO triangle output to provide pulse-width modulation.

These modulatory activities certainly help to animate the sound of the Syn-Bow, but pulse waveforms are pulse waveforms and the lack of other waveshapes is a considerable sonic limitation.

There are actually three VCAs in the Syn-Bow. One, on-board the SN76477N, operates connected to an envelope generator providing a simple attack and decay cycle. The attack time is controlled by a fixed resistor connected to the relevant pin on the chip, the decay by the front panel decay control. The second is a diode VCA connected to the audio output of the SN76477N and controlled by the voltage from the touch sensor. The third VCA is a CA3080 transconductance op-amp actually used as a non-linear transformation block, which means that the waveshape passing through it alters according to the amplitude of the input signal. Since this amplitude depends on the voltage from the touch sensor, it follows that the touch sensor also affects the waveform transformation. Blacet call this third VCA their "natural filter patch", the idea being that it should enable the Syn-Bow to mimic the behaviour of natural instruments and louden, brighten and increase the sustain of a waveform the harder the pressure applied to the touch sensor.

This is a pretty clever idea, but the amount of touch variation of waveshape isn't that great and doesn't disguise the square wave pedigree of the original SN76477N output. It's curious that Blacet haven't also added a proper VCF to provide some rather more extensive timbral transformation.

The weakest link in the system is the fact that the attack and decay parameters are preset; what's really needed in an instrument like this, especially if one's taking touch control to its logical conclusion (and this is where the ondes Martenot steps in), is to make attack and decay time totally dependent on how the touch sensor is initially hit and how long the fingers stay on the sensor. Instead, if a short decay time is set with the front panel control, one is forced to retrigger every note played, which gives a very unnatural choppiness to the sound, or, if a long delay time is selected, notes played include all the intervening slides of the frequency bow.

The use of the frequency bow is no easy matter, as it's probably more akin to plucking notes out of thin air than any other fretless or keyless instrument (with the exception of the Theremin). However difficult conventional fretless instruments may be to learn initially, at least the notes are available on the basis of linear spatial coordinates, i.e., notes stretch in a line in front of or away from you. With the Syn-Bow it's necessary to choose your notes out of a circular distribution and that really is incredibly difficult, especially when you're at the top end of the instrument.

The Blacet Syn-Bow is available from Blacet Music Research, (Contact Details). The current price of the kit is $124 and UK residents should add a further $10 for shipping. Customs duty and VAT will add a further $30 on top of that. So, at an exchange rate of $1.85 to the pound, a Syn-Bow will cost you about £88. Is it worth it? Well, considering that it's a kit, a nd that the components could be conservatively bought for about £25, it does seem over-priced, but, for anyone interested in exploring alternative methods of synthesiser control, it does offer much food for thought.