Roland SPV355

The SPV355, launched in the late '70s, was intended to allow the pitch of instruments such as guitars and saxophones to control analogue synth sounds — which it does with varying degrees of success. Fortunately, it has other tricks up its sleeve, as Chris Carter explains.

The late '70s were exciting times for analogue synthesis. MIDI was still a few years away, and legendary names such as Moog, EMS, Serge, Oberheim and Sequential were releasing innovative and exciting gear.

But it was Roland that always had a special place in my affections, and much of my early years were spent lusting over Roland catalogues... yeah, me and Roland go back years. Hanging out at Rod Argent's and Macari's music stores in London's West End, tinkering with the new Roland gear while trying to convince sales staff I was a serious buyer. Little did they know I was on my lunch break with just a few bob in my pocket and only a couple of quid in the bank. Roland were on a roll: Bossa Nova‑stylee drum machines and weedy‑sounding keyboards were a thing of the past, and seriously specified analogue synths and studio gear were appearing on a regular basis. Those were the days...

The Roland Rack

The three‑way input selector switch sets the P/V Synth to operate with either Guitar, Voice, or Woodwind/Brass instruments. Unfortunately, even with the best will, results with a guitar are unpredictable!

The SPV355 Pitch‑to‑Voltage Synthesizer was launched in those very days — 1979, to be exact — as part of the Roland Rack series of 19‑inch studio–quality effects units, amplifiers and specialist preamps. The most famous of these are probably the Roland Vocoder and the Dimension D spatial chorus. The P/V Synth is a bit of a curiosity, because it seems to have been released on the one hand as a rackmounting analogue expander module (indeed, it's said to be one of the first rackmounting synths), but on the other as a budget alternative to the Roland GR–series guitar synthesizers. These synths were quite expensive, specialised instruments; the GR system consisted of a high‑quality, specially adapted guitar connected via a 24‑way cable to a floor unit containing a rudimentary, six‑note polyphonic synth engine. The SPV355 alternative scored points as it didn't need any special interface hardware (pickups and so on) and you could, in theory, use any old guitar to play the synth. The 1979 Roland catalogue states: "The SPV355 P/V Synthesizer is specially designed for use with guitars", which is ironic, as this is probably the P/V Synth's least effective and most problematic mode — more on this later.

Fortunately, the SPV335's uses were not confined to guitar synthesis, and for its time (and compact size), it was quite well specified: two VCOs, a sub‑oscillator, VCF, VCA, envelope generator, two audio mixers, and a multitude of interface sockets. As with other Roland Rack units, the 355 is housed in a 2U steel case and weighs nearly 6kg, which makes it a pretty hefty beast to lug around. And as for build quality, well... the word 'tank' springs to mind, as does the phrase 'heavy duty'. They don't make 'em like that any more...

Pitch To What?

The Dual VCO section allows two different tunings to be set up for oscillator 2. It's then possible to swap between these tunings via the A/B footswitch socket.

The 'P' of the P/V Synth's title stands for pitch, and the 'V' stands for voltage — but what is this scary pitch‑to‑voltage technology they speak of? Well, its main function is to translate an audio signal, from an instrument such as a guitar, voice or wind instrument, into musically‑related control voltages and triggers capable of playing a CV/gate synthesizer. The SPV355 does the translation and uses the voltages to play its own internal synthesizer.

There are a couple of points to consider when using a pitch‑detection system: they can't decipher chords, and they have a hard time with harmonics. Unfortunately, these are two things at which the guitar excels. The SPV translates solo voice and some woodwind instruments quite well, but guitars, even playing single notes, can give rise to jumpy, unstable pitch‑tracking, especially if the sound contains complex tones. You have to keep it basic, clean and monophonic — but then you might be surprised at how accurate the SPV355 can be.

Well Specified

The SPV's uncluttered rear panel.

The SPV's front end starts off with the Input (pitch detector) and a three‑way switch for selecting input signal type: Guitar (pickup), Voice (microphone) or Brass (transducer). There are a couple of useful LEDs to indicate activity — green for Gate triggering and red for audio overloading — plus a Threshold control for adjusting the Gate trigger sensitivity to the Envelope generator. Too high a setting will produce spurious multiple triggering; too low and you'll end up with ignored or missed notes.

The synth's dual (monophonic) VCOs are switchable over three pitch ranges (4', 8' and 16'), and each VCO can generate Saw, Square and Pulse waves. Unfortunately, both VCOs share the same controls for Range, Waveform and Tune. However, VCO2 also includes an additional, footswitch‑controlled A/B tuning function, which makes it possible to offset its tuning relative to VCO1 by up to plus or minus one octave. VCO1 also has a separate square‑wave sub‑oscillator output (at minus one octave), and all three outputs (VCO 1, 2 and sub) are fed into Audio Mixer 1, which allows one to create some interesting tones and textures by mixing the outputs of the three oscillators in varying amounts. A footswitch‑controlled variable Portamento function is available for the VCOs, but unfortunately this only works internally and not when they're under external CV control.

The SPV355 features a well‑specified voltage controlled filter, a 24dB/octave type with a range of 10Hz‑20kHz and the ability to self‑oscillate, in which case it becomes a third VCO. It has the usual Frequency and Resonance controls but also includes sliders for Pitch Follow and Envelope modulation depth; usefully, both of the last work in positive and negative directions, for inverted or reverse‑type effects. The VCF is one of the P/V Synth's jewels, and gives it a lot of its character. Like the filters on many Roland synths of the time, it sounds sweet and musical, and very analogue — it's just a shame that there isn't a way of feeding external audio through it.

The VCA section is minimalist, with just a single switch to select control via the Envelope Follower or the Envelope Generator. The Envelope Follower works by generating a control voltage that closely follows the amplitude of the input signal. It has no controls itself, but altering the Input Threshold control has an effect on the level of the Envelope Follower — the Threshold control works almost to set depth amount for the EG. The Envelope Follower CV signal can modulate both the VCF and VCA, and is also available via a jack socket on the rear interface panel, to be used as a control voltage source for external devices. Mine's hooked up to a voltage‑controlled phase shifter at the moment. The EG is an ADS (Attack, Decay, Sustain) type, without the usual Release function. This doesn't make much practical difference to the kinds of sounds the SPV can produce, and in fact the EG is extremely good at shaping short, punchy bass and similar envelopes. If I were the cynical type I could suggest Roland omitted a Release stage because of the inherent pitch drift that shows up when you use the Pitch Hold function (see 'CV/Gate Hold' box), but hey, this was before digital...

Using The P/V Synth

Using the P/V Synth successfully with a guitar requires a lot of patience, plus a pretty unnatural style of playing. I have to admit that I've rarely used it this way, the main reason being that I'm not a guitarist, but even my partner (who is a guitarist) gave up on it years ago. More satisfying results can be achieved with voice and brass. But although I've used the SPV355 live on a number of occasions I couldn't really recommend this, unless you're playing experimental music, because of the synth's tendency to unpredictability and instability.

Fortunately, although its main purpose in life was intended to be pitch‑to‑voltage conversion, the SPV355 doubles as a very good and very hands‑on analogue expander module. The relative simplicity of its operation and editing means that it needs no menus or multi‑mode switches, and with its versatile interfacing options it integrates well into most old and new CV/gate‑based modular systems and setups. (With the help of a sophisticated modern MIDI‑CV interface, such as Kenton's Pro4, it should also be possible to access most of the SPV's capabilities via MIDI.) It's ideally suited, too, for partnering something like a Roland SH101 analogue monosynth, or even a Roland Vocoder, for real‑time synth pitch following (see 'Using The SPV355 With A Vocoder' box for more details). Admittedly, it lacks a few useful features, such as independent waveform controls, a Noise generator and an LFO (although many MIDI‑to‑CV converters have built‑in LFOs), but with its dual VCOs, sub–oscillator, well‑specified VCF and logical layout, the SPV355 is very good at quickly producing bass, lead and authentic analogue synth sounds with plenty of character and bite.

Things To Make And Do

Almost because it's such an oddball, the SPV355 can be used in a variety of interesting ways. For example, it can take on the role of a rudimentary MIDI‑to‑CV converter, by virtue of its pitch‑tracking function. Connect the audio output of a MIDI synth to the SPV, play a line (manually, or via a sequencer), and the SPV can extract its pitch and convert it to a control voltage, which in turn can play an analogue synth with a compatible CV input. Synth sounds are very suitable for SPV355 pitch–tracking, as the feature works best when driven from a clean, strong (monophonic) signal. The SPV355 will respond surprisingly accurately to vibrato, pitch‑bend and portamento contained in the audio signal, although the SPV's own portamento will probably work more effectively. (The best thing is probably not to bother with portamento on your synth, and have it set on the SPV instead.) Sounds that are rich in harmonics, below 70Hz, or in the very high kHz range, are best avoided, as they will introduce noticeable tracking errors.

Voices are also fun to work with, off tape or live, and I've often found that the cheaper the microphone used, the better the results. I use an old Coloursound dynamic mic through a preamp for the most accurate pitch and envelope tracking. A few lines of wordless 'doo wop wops' can be transformed into very effective bass lines or sequencer patterns, particularly after a few effects are added. Just make sure you're recording to tape or hard disk as you go along; this kind of 'on the fly' experimentation is hard to reproduce at will. Feeding spoken dialogue (taped or otherwise) into the SPV355 is also an interesting way of generating seemingly random pitches, gate triggers and envelope signals. You can even connect a drum machine to the SPV's audio inputs, and this creates some interesting and strange results. Cymbals and snares don't translate too well, but some bass drum, tom and short percussion sounds can produce very usable effects.

As mentioned elsewhere, the SPV has five front–panel performance control sockets: Portamento; VCO 2 A/B; CV/Gate Hold; Mix/Direct, which switches the direct input signal in and out of the audio chain; and VCO/VCF Sensitivity, which adjusts how much the input signal is modulating the VCO or VCF, via a variable foot controller rather than a footswitch. These sockets are primarily meant for use with footswitches and pedals, but if you have access to a CV/gate modular system it's worth experimenting with controlling these functions automatically from sequencers, triggers, gates and LFOs. Similarly, the rear Pitch CV/Gate and Envelope Follower CV outputs can be used to govern the functions of all kinds of other analogue–controlled modules.

Finally, if you're handy with a soldering iron, take a bare jack plug and solder a small on/off toggle switch to the earth and tip tags. Make a couple of these 'jack switches' and they can be used instead of foot switches in the front‑panel sockets, to directly select the features mentioned above.

Impulse Power

I bought my SPV355 on a bit of an expensive whim, after seeing a very polished Roland demo involving a guitar and a saxophone (if I remember rightly). Although since I'm neither a saxophonist or a guitarist I'm not sure what was going through my mind at the time! Within hours I had it hooked up to a tape deck, a microphone, a drum machine and a Roland 100M modular system — in fact, anything with an audio output or CV/gate connections.

Over the last 20 years the SPV355 has become an integral part of my analogue modular system, along with my Dimension D chorus, and apart from a few racking scratches is almost as good as the day I bought it — but then I've only used it live a couple of times. Ten years ago it was serviced, mainly to tighten up some excessive pitch‑drift. This drifting effect is quite common in the SPV355, but fortunately is only apparent when using the CV/Gate Hold function in P/V mode. When controlled from an external CV/Gate control source, used as an analogue expander, I've always found the P/V Synth to be stable and accurate, and eminently capable of producing a wide range of classic analogue synth sounds without much effort. In fact, it's almost everything a good analogue synth should be.