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Which Synth?

A comprehensive guide to features and capabilities

With so many models on the market, how do you know which one to buy? There is no easy answer, but here E&MM tells you what you can expect from individual features and on which synths these can be found.

The term 'synthesiser' covers a host of different instruments, occasionally used inappropriately or even incorrectly by manufacturers, retailers and consumers. Clearly it would be impossible to cover everything that is loosely termed a synth. For the purposes of this feature (particularly the comparison chart), synth is taken to refer to oscillator/filter/envelope-based subtractive synthesis machines, played from a conventional keyboard and programmed with a front panel laid out to give access to the individual elements of sound creation. The only other criteria is that the instruments are readily available, first-hand, in assembled ready-to-play form in British shops.

It is therefore essential to briefly mention some of the exclusions to our table and the reason for their omission. The new Yamaha DX range represent excellent value-for-money and a high standard of sound quality. They do not however function on the subtractive synthesis principle but on FM technology and therefore can only be compared with the synths featured in terms of sound (a subjective judgement for the reader's own ears). There are many multi-purpose keyboards on the market which feature a synthesiser section (Korg Trident II, Crumar Composer, Trilogy and Stratus) as well as many string and brass synths, all of which are useful machines, particularly in terms of a big sound or a single versatile keyboard. All however suffer in terms of scope or access to individual elements of the sound creation and are therefore not treated here.

Many excellent synthesisers of the past are for one reason or another no longer readily available in shops and are omitted to avoid creating any demand for non-existent machines, and for the same reason new models on their way (Prophet T-8, Rhodes Polaris, Siel Opera 6, Voyetra 8) have not been included. Synths built from kits (Powertran, Maplin, etc.) often represent a huge saving to the buyer without loss of quality, but again they require a certain time and skill to build hence their omission.

We should point out however that by obtaining the specification of any synthesiser, the features stated can be compared to those in our chart and an idea of the flexibility and suitability to the buyer's need of that particular model can be formed.

When considering purchasing a synthesiser, it is vital to decide firstly the role it will be required to play and from this to establish an order of priorities in terms of features. If you particularly need to play polyphonically, then you may decide to sacrifice flexibility for a larger number of voices, and if you are not as interested in learning to program as in having a good selection of sounds, you might opt for a preset only machine or even a personal keyboard or ensemble. If the ability to change sounds quickly (eg. in a 'live' situation) is more important than total flexibility (say in the studio), then a machine with programs at the expense of features is the answer.

To aid this decision, we have detailed the basic elements of subtractive synthesis and overleaf you will find a chart breaking down the features of such synths into these individual elements. To permit analysis of the chart and how it relates to your needs, here is an explanation of the function of each element, the uses it can be put to and the abbreviations used in the table:

Keyboard: The main interface (in real time performance) between the player and the instrument, must be tried to form a definite opinion, but here are some guidelines. Clearly a longer keyboard is necessary for full polyphonic playing, whereas a monophonic can cover a large range by use of the footage control. Most keyboards are based on a C scale (C to C, or F to C) and are plastic, but some of the latest products aim for a more piano-like keyboard, using wood and/or touch sensitivity for extra familiarity and control from the keyboard.

Voices: Monophonic or polyphonic, this is perhaps the biggest decision you have to make. To obtain the same features polyphonically can cost you 5 or 10 times as much as a similar monophonic set-up, and in opting for polyphony under £1,000 you are inevitably going to limit your flexibility. However, it can be seen from the chart that several synths offer a choice on this score. The Korg Mono/Poly can be mono-, duo- or quadrophonic, and as such makes a good choice for an all-purpose synth, particularly in the studio, but again loses true flexibility in poly modes. *The Oscar has a duophonic assignment ability which is particularly useful for playing along with the sequencer (normally only possible on polyphonics). 6The Rhodes Chroma has numerous internal set-ups (called algorithms) which give total freedom in the assignment of oscillators to voices.

Oscillators per Voice: The number of oscillators played by any one note determines much of the sound. Two or three oscillators can be set at different octaves (a sub-oscillator is a good compromise here) or fixed intervals. Slight de-tunings between oscillators give a much richer sound introducing 'beating', although Chorus and PWM can both be used to fatten up the sound (see these headings). VCO stands for the original analogue Voltage Controlled Oscillators which have a rich sound, but need a periodic Auto-tune or manual readjustment. DCOs (Digitally Controlled Oscillators) are software-generated, crystal derived and need no tuning but they can sound thin if PWM, chorusing or 'overdrive' is not available.

Waveforms on Oscillator: These are responsible for the basic timbre of the sound as they each have different harmonic content.

The triangle wave gives the fundamental with little harmonic content as it resembled a sinewave (pure fundamental). Some synths actually give a pure sinewave, but this is quite easily obtained by close Low Pass filtering from any waveform. Gives a pure 'flute' sound unfiltered.

The sawtooth wave contains all the harmonics in inverse volume to their number (ie. the higher they are, the quieter they become). Gives a fat 'brassy' sound unfiltered.

The square wave contains only the odd harmonics, which gives a hollow 'oboe' sound.

The pulse wave has a different harmonic content depending on the width of the pulse (which is almost always variable except on the Roland JX3P). If the width is half the wavelength then of course we have a square wave. As the pulse gets wider or narrower (the effect is symmetrical), the high harmonic content increases as the fundamental weakens.

Pulse Width Modulation: automatic control of the pulse width of oscillator waveform. The effect created is a richer moving sound, particularly effective in lower registers. On some instruments this is available as a choice on the waveform select, whereas on others it must be routed through an LFO or ENV (envelope), or controlled by the other OSC (oscillator).

Osc. Sync. This feature causes the second oscillator to begin a new cycle every time the first oscillator does. This synchronisation means that oscillator 2 can only run at the same frequency as oscillator 1 or a harmonic. In combination with glide this can give interesting harmonic sweep effects.

LFOs. Low Frequency Oscillators are used to create regular modulation effects, such as vibrato, trills, tremolo, PWM etc. It is often possible to use Osc 2 or Osc 3 as an LFO but this negates audio use. As different modulations require different speeds it is useful to have 2 LFOs, especially if sequencing or arpeggiation speed is controlled by an LFO as well (Seq/Arp).

As some effects (vibrato for example) sound a bit odd as the note is played, it is also handy to have a delay control, or if the modulation is brought in afterwards by the joystick.

Waveforms on LFO: Some LFOs are unmarked, which means that they are triangle wave or sine wave only.

The triangle wave gives an even modulation up and down useful for vibrato, PWM etc.

The rising ramp wave gives a slow attack modulation suitable for 'backwards' effects.

The falling ramp wave gives a sharp attack modulation suitable for rhythmic effects.

The square wave gives two distinct levels. Ideal for trills.

S/H: Sample and Hold or Random, changes the level of the LFO at regular intervals but by random amounts. This is particularly effective if used on the filter as a rhythmic device.

Keyboard Track determines how much the pitch of the note played moves the filter cut-off frequency.

Full, On or 100% means that the frequency of the filter goes up in direct proportion to the oscillator frequency. This means that the timbre of the note stays exactly the same. More than 100% means higher notes are brighter, less means the lower notes are brighter. 0 or Off or nothing means there is no filter frequency movement with notes. Negative amounts attenuate the higher notes drastically. Continuously variable tracking (shown by the word to) means that you can actually 'tune' the keyboard follow to the required amount on upper notes, having set the sound on lower ones.

Filter Type(s): On synths with a choice, this enables you to choose various filter modes.

Low Pass attenuates the frequencies above the cut-off point, low frequencies are unaffected.

Band Pass attenuates the frequencies above and below the cut-off point.

High Pass attenuates the frequencies below the cut-off point, high frequencies are unaffected.

A 24dB/oct effect gives a sharp cut-off, a 12dB/oct cut-off gives a less pronounced effect and 6dB/oct is very slight. On some synths you can alter the cut-off slopes but on most these are fixed and contribute to the overall sound of the synth.

Ring Mod. (or effect): A ring modulator is a circuit which produces the sum and the difference of all the frequencies of the inputs. This gives harmonically-unrelated frequencies which are very useful for making 'bell' or 'plucked' sounds. If the circuit itself is not available, it is often possible to create the effect by using Polymod or Cross Mod sections, or an additive synthesis section (waveform creation).

Glide Types: Any of the following are possible.

Gliss: glissando causes the pitch to slide smoothly from the last note to the new one.

Port: portamento causes the pitch to jump in semitones from the last note to the new one.

Man: manual means the glide effect only happens when last note is still held (legato playing).

Auto: automatic means effect always happens.

Poly means glide effect works in polyphonic mode.

Mono means glide effect only works in unison mode (see this column).

Fixed T or R allows you to choose whether glide happens at a constant rate (the usual way) or in a fixed length of time.

Envelopes per Voice: if you only have one envelope per voice then it is not possible to get independent filter and envelope contours which is limiting to more complex sounds. The four possible envelope controls are attack, decay, sustain and release and they are referred to as A,D,S and R, so an AD has only attack and decay controls.

Performance Controls: these permit 'real time' pitch bends or modulations to be controlled in performance, essential for adding expressions and character to the playing. Wheels allow bends and modulations to be controlled independently, whereas a joystick means that the two can be executed together. The Yamaha CS-01 has an additional breath controller (BS-1) available which means that both the Filter and Amplifier can be controlled by blowing. If the wheel amounts are programmable it means that they can be adjusted to suit your individual preferences.

Noise Source: can be either White or Pink. On some synths noise actually replaces one of the oscillators (r/Osc) which can be a little limiting.

Hold keeps the envelopes open indefinitely after they have been triggered. This means that the synth will continue to play itself after the key has been released.

Uni: (unison) only applicable to polyphonic instruments. Turns the instrument into a monophonic with all the oscillators triggered by one key. Gives a very 'fat' sound and is ideal for lead lines and solos.

Arp.: (arpeggiator) an increasingly popular feature on both monos and polys. Causes the notes held to be played in an arpeggiated fashion. Possible ways of playing are Up (U), Down (D), alternating up and down (UD) or assign (Asg) ie. in the order the notes were played.

Crs. Set.: (chorus settings) chorus effects are also more common, particularly useful for ensemble sound such as strings and choirs.

Sequencers: The capacity of these is expressed as a number of notes for each sequence (X) or shared between the sequences (÷). A Real Time sequencer plays back the notes exactly as played, whereas Step Time has to programmed one note or rest at a time. If there is no division between the columns it means that the capacity is shared between step and real time.

Programs: these allow you to store patches made on the panel to be recalled for future use.

Pre. (presets) are patches made at the factory which are permanently stored and cannot be overwritten.

Mem. (memories) are storage locations for the user to keep his own patches stored. Some synths come with factory presets in memories which can be over-written. Where this is the case the number of programs is in the middle of the two columns.

Cass. Dmp.: (cassette dump) this allows program and sequence information to be stored in digital information on cassette tape. This allows valuable presets to be safeguarded and leaves storage space in the synth free for further creative use.

External Controls: These are inputs and outputs which allow the synth in question to be used in conjunction with others, with sequencers or with computers.

In allows the synth to be controlled externally.

Out means the synth can control others.

Through means the synth can be used in a chain.

Tr (trigger) is a signal which opens an envelope or clocks an LFO (seq/arp).

G (gate) is a signal which holds an envelope open for an appreciable time.

C.V. (control voltage) is a (1 volt/octave scaled) voltage which determines the pitch the oscillators should play.

DCB (digital communication bus) is a Roland connection which allows the MC4 (sequencer) to operate with their synths.

MIDI is a universal interface system developed by Sequential Circuits to facilitate interconnections between synths, sequencers and computers.

Now we have explained the relevance of all the columns and abbreviations used, the chart is below. You will see that some products by the same manufacturers occupy the same row. This is because many of their features are the same. In the sections where they do differ they are separated by a dotted line. Otherwise they share identical features and the same box in the chart.

Which Synth? — A Comprehensive Guide to Features and Capabilities

(Click image for higher resolution version)

Companies mentioned:
Elka-Orla (UK) Ltd., (Contact Details).
(Jen) (Contact Details).
(Korg) (Contact Details).
(Moog) (Contact Details).
(Oberheim) (Contact Details).
OSC (Oxford Synthesiser Company), (Contact Details).
(Rhodes) (Contact Details).
Roland (UK) (Contact Details).
SIEL (UK) Ltd., (Contact Details).
Synton, (Contact Details).
Yamaha/Kemble Ltd., (Contact Details).

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Jethro Tull's Peter Vetesse

Electronics & Music Maker - Copyright: Music Maker Publications (UK), Future Publishing.


Electronics & Music Maker - Sep 1983


Buyer's Guide


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