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Create sounds using analogue electronics (Part 10)

Posted: 22 Aug 2012     Print Version  Bookmark and Share

Keywords:Step sequencers  analogue synthesisers  CV  gate 

This exacting process, particularly for polyphonic music, could be very time consuming, and editing was primitive with a display that showed just the note time position, pitch, gate and CV details for one note at a time. Storage was on tape cassettes.

Simpler stand-alone dedicated CV and gate sequencers followed, but difficulties with interfacing computers to CV- and gate-based analogue synthesisers meant that it was not until MIDI that general-purpose computers really started to play a role as sequencers. Once MIDI has become widely adopted, and computer-based MIDI sequencers were developed, then MIDI-to-CV/gate converters were used to enable analogue synthesisers to be controlled by a MIDI sequencer.

It is worth considering the number of cables and converters that may be encountered in an analogue synthesiser sequencing environment. The synthesisers will probably have a power supply cable, plus one or more audio output cables. CV and gate cables might be augmented with additional CVs to affect filter cut-off or envelope decay/release time.

Synchronisation of a sequencer with a tape recorder, video playback, drum machine or other sequencers might require the use of standards like DIN-Sync 24, which was used before MIDI to provide synchronisation with 24 pulse-per-quarter-note timing signals, plus a start/stop signal, or MIDI Time Code or conversion between them. One volt/octave and exponential CV systems might require conversion, and there were several different 'standards' for what constituted a gate signal, with corresponding converters.

Recording analogue synthesisers needs to take into account a number of challenges. First, because of all the cabling, it is very easy to get ground loops which can cause hum. Tuning stability can also be a problem, and so waiting for internal temperatures inside the synthesisers to stabilise after power-up, and then frequent tuning, may be required, even in a temperature-controlled environment.

Most analogue synthesisers have mono outputs and so need to be panned or fed into two sets of comb filters to provide positional information in a mix, and they may sometimes require gating to prevent noise from escaping into a mix. In addition, the wide usage of low-pass filters in subtractive synthesisers can result in a mix becoming bass heavy, and a little high-pass filtering can help to remove this.

To produce polyphonic sounds from monophonic analogue synthesisers, you need either several synthesisers or to record the same one several times (tuning!). This can have unexpected side effects: slightly different rates of glissando, portamento or LFO modulation can sound very impressive.

Analogue synthesisers also have either limited effects (chorus in string synths) or none at all. Adding external effects to a synthesiser can produce a number of effects: echoes set to almost the clock rate of a step sequencer will produce syncopated rhythms that almost repeat an interesting contrast to the exact and predictable timing produced by digital synthesisers or computers with tempo-synchronised effects.

Using just the pre-echoes and turning off the rest of the reverb, or vice versa, can be interesting too. Adding distortion to monosynths (polysynth chords tend to just produce noise) and playing guitarinfluenced melody lines can produce a very distinctive sound.

To be played in context, synthesisers should be arranged in stacks, with a synthesiser on top of a string machine, on top of an organ or electric piano. Two-handed playing on different keyboards was much more common than split keyboards, except for the lower-cost multi-keyboards which mixed strings synths a VCF-based brass effect with a monophonic bass. Having two separate sounds and no restriction about which hand plays high or low parts (or both simultaneously) can be an interesting challenge, and one that can undo the legacy of piano lessons.

Early analogue synthesisers do not have memories for the sounds, and so the performer needs either to have multiple synthesisers or needs to change the sounds during performance. Given the cost of analogue synthesisers at the time, performers learned to change the controls to create different sounds. This required practice and a good familiarity with the synthesiser's layout and controls. Commonly changed parameters for these 'fast edits' include the VCO waveforms, VCO2 detune, VCF cut-off frequency and resonance, attack time and decay time.

Because analogue synthesisers normally have live controls, parameters would often be changed during the performance, and so if any of the settings were not right, they would be changed with one hand whilst playing with the other. MIDI controller boxes and DJ controllers are the modern equivalent of this live parameter adjustment from the 1970s.

Analogue synthesisers abound in clichéd sounds (some might say nothing but), although fashion and retro are cyclical, and if this is seen as bad, then waiting awhile may reverse the situation. Clichéd sounds can be used to advantage by avoiding the other clichés contextual sounds of the time: syndrum sweeps, spring-line reverbs, classic electronic drum sounds and 16-step sequencer bass lines (or by deliberately using all of these).

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