All For One And One For All
Looking for the hardest, heaviest, thickest and fattest analogue synth line? Strictly monophonic? Step this way, because Peter Forrest is about to unveil his unique guide to the analogue synthesiser’s unique feature: Unison Mode, in which all the oscillators gang together and hit you over the head
Unstable oscillators, frequency drift, phase differences... it's all grist to the mill in Unison Mode...
With all the interest currently being shown in vintage analogue polysynths it's interesting to consider what it is about their sound that made/makes them (sometimes) so wonderful. Part of the secret is tuning imprecision: the fact that analogue oscillators are often very slightly out of tune even when they are 'in tune'. It's an effect used to best advantage on instruments which offer some sort of unison mode - the ability to stack all the oscillators together and play them monophonically.
In this way, differences in phase and slight tuning discrepancies between the waveforms of individual oscillators combine to produce that classic half chorus, half sync, half phasing sound, - yes, you guessed it, a monosynth sound and a half!
A surprising number of vintage synths can manage this little trick. Among them are the Bit range, Kawai's SX210 and SX240, Korg's MonoPoly and Polysix, the Memorymoog, most of the Oberheim range (except for the Matrix 6), the Voyetra Eight, Rhodes Chroma, all the Roland Jupiters, all the classic Sequential Circuits analogue range, and even Yamaha's strange CS70M.
On each of these synths, it's possible to set all the oscillators to play a single monophonic line. Indeed, on Sequential's two monsters, the T8 and Prophet 10, you can split unison sounds available, with four and five voices respectively in each half of the split. On some instruments - the Prophet 5 and the Oberheims, for example - all that's necessary is to press the button marked 'Unison' (or 'Mono' on the Memorymoog); on others you have to do a little more work. For instance, on the MultiTrak and SixTrak, I think I'm right in saying you have to create a 'super-stak' out of six versions of the same sound.
Just to confuse matters, the Roland JX8P introduced its own peculiar terminology in this area, where 'unison' refers to turning the synth into a 3-voice, 4-DCO per voice instrument. While 'solo' is the function you select if you want the standard unison effect. The same applies (with more oscillators) to the JX10 and MKS70.
It's worth pointing out that although synths with digitally controlled oscillators (DCOs) like the JXs, the Bits, Kawai's and Oberheim's Matrix 1000 do provide a unison mode - which in itself can be very effective - it cannot really compare with the classic unison sound on all-analogue machines. The reason for this is quite straightforward: though DCOs actually produce an analogue waveform, their pitch is controlled digitally. This means that you can rely on them being exactly in tune and remaining that way irrespective of time, temperature or fluctuating mains voltage. The down side, however, is that you get none of the 'movement' and warmth associated with their voltage-controlled predecessors.
Even a synth with the degree of control offered by the JX10 can only 'spread' the oscillators by a fixed amount to give the sound a little more breadth. Where the VCO-based instruments are concerned, it is the continual slight changes in the frequency throughout the duration of a note that gave them so much of their power.
If you've never heard a synth in unison mode, it's not easy to describe the effect in words: powerful, fat, meaty, flanged, full, heavy... These adjectives only go some of the way to evoking what is a very distinctive sound. In somewhat less charitable mood, you might also add 'overblown' to the list - and used in the wrong place, or to (the wrong kind of) excess, this may well be the case.
Clicking into unison mode isn't a universal panacea. You can sometimes lose the power inherent in a great patch rather than adding it. It all depends on the way the waves interact. If it happens that some of the phase differences cancel each other out, then you're bound to lose something. If you've ever spent time with a Minimoog, you'll understand the problem: sometimes a great sounding patch using two oscillators can actually deteriorate if you bring the third VCO into the equation as a sound source rather than a modulator.
If the same thing happens when you switch to unison mode, there's a simple solution: don't use it! There will be plenty of other occasions when an innocuous or downright weedy sound can be given a radical hormone implant by switching into unison. Take the Korg Polysix. Not exactly in the premier league of absolute classic polysynths, but it can put out some really meaty lines in unison mode. The Prophet 5 is a blaster, too, and so are the Oberheims - particularly with the pitchbender pulling one of the sets of oscillators out of tune. Pure funk.
The OB8 even has the controls for fine tuning the oscillators easily accessible on the side panel - great for tweaking them in real time. But there can be no doubt that the king of the unison synths is the inimitable Memorymoog: 18 Moog oscillators screaming away on a single line. Enough said..?
On the second-hand market, there hasn't traditionally been a huge difference in price between, say, an OB1 and an OB8, or between a Minimoog and a Memorymoog. But that's definitely changed in the last year or so, and rightly so in my opinion. If there isn't any significant difference in price between a monophonic and a polyphonic with unison, I know which one I'd go for - every time. Bearing in mind the notorious unreliability of older synths, you've always got other voices to fall back on if one gives up the ghost!
If you're looking for a source of unison sounds at a budget price, check out MT's Readers' Ads for a MonoPoly (£100 -£240) or Polysix (£150 - £300), a Jupiter 6 (£400 - £500), a SixTrak (£150 - £240) or MultiTrak (£180 - £270), or possibly a Prophet 600 (£200 - £400). If you're looking for the best unison sounds at any cost, then watch out for the fast appreciating Prophet 5 (£500 and upwards) Oberheims (£400 and upwards) and Memorymoog (£800 and upwards).
Personally, I believe that if unison mode synths (and analogue VCO polysynths generally) had never existed, they'd create as much of a stir being released today as did the DX, Fairlight, D50, M1 and Wavestation on their release. Come to think of it, I can't understand why E-mu didn't include more Prophet and Oberheim unison sounds in the samples they used for their Vintage Keys module. Maybe they just don't like them as much as I do!
Feature by Peter Forrest
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