Basic Sound Synthesis: Part 7 – Miscellaneous Stuff

Monophonic/Polyphonic: Early synthesizers were only capable of producing one note at a time, but through evolution of technology they became more and more powerful (and cheaper to produce), to the point that modern synthesizers can play a near-infinite amount of notes simultaneously (like a piano). However, most synthesizers still have the option of playing in a monophonic or polyphonic mode. Quite simply, a monophonic (think ‘mono’) synthesizer can only play one note at a time, and a polyphonic one can play two or more. The monophonic setting can be useful for some lead and bass sounds, as it prevents two keys from being held down accidentally and overlapping each other. Portamento/Glide: Gives the ability to slide between notes. The effect of portamento is best used on monophonic sounds to create a bending between notes, but can also be used polyphonically when played in the style of block chords. The time (and occasionally scale) of the glide effect can be changed, allowing...
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Basic Sound Synthesis: Part 6 – Arpeggiators and Sequencers

Arpeggiators and sequencers have been part of synthesizers since the 1970s, when basic patterns could be played without having to manually press the keys down, allowing complex melodies to be played with 100% accuracy at any speed. Nowadays, sequencers and arpeggiators have become infinitely more complex, mostly due to the fact that they are programmable from a software interface, where a whole song can easily be programmed with a MIDI keyboard and a mouse. The arpeggiator or sequencer built into your trusty synthesizer is not to be ignored however, and the following information will hopefully give you some idea of the power such functions posses. Arpeggiators are designed to create small melodic patterns from the notes the player gives the synthesizer. For example, the user may hold down the C, E, and G keys on the synthesizer, and with the arpeggiator active it would repeatedly play the selected keys in various different ways depending on how it was programmed. Arpeggiators can...
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Basic Sound Synthesis: Part 5 – Effects Part 2

Distortion: A popular effect when used on electric guitars, distortion is the process of boosting the synthesizers signal over the limit, to the point where it clips and can remove parts of the audio range. It is also possible to distort signals so that additional harmonics in the frequency range are created. Distortion, or ‘overdrive’, are not common effects used on synthesizers due to the unpleasant clipping of the signal, although used creatively it can produce interesting effects. Phaser: In phasing, the signal is fed through an all-pass filter which creates peaks and notches (highs and lows within the frequency spectrum). When done statically, this creates modifications in the signal from the synthesizer, but to create a moving effect an LFO is used to sweep the comb filter, creating the standard phaser sound. Phasers can be used in various different stages, such as 2, 4, 6, 8, 16, or even more, with the more stages being used the more effective the...
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Basic Synthesis: Part 4 – Effects Part 1

Effects, while not technically a stage of any form of subtractive music synthesis, are commonly found on the end of most signal paths from synthesizers. Effects can come in an internal form (built into your synthesizer), and in an outboard form (where it is a separate effects box, such as a rack mount unit or pedal). While internal effects are useful parts of synthesizers as they save on space and power, they are usually not as high quality as a dedicated external effects unit, but will suffice for most users. Bear in mind when purchasing a vintage synthesizer, that many older models (from the 1970s and 80s) will most likely not have any form of built in effects. Unison: In similar fashion to effects not technically being part of sound synthesis, unison is not really an effect, but more of a fixed option within your synthesizer. The effect of unison is simply to multiply the signal which is being produced by...
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Basic Synthesis: Part 3 – Envelopes

Envelopes are the key to the articulation of your sound. Without them your patch will immediately start off at full blast, and stay there, and then disappear all of a sudden when you let go of the key. Envelopes, although difficult to understand at first allow you to change that, so you can create expressive and dynamic sounds with your synthesizer. The standard envelope is in 4 main stages, described below: Attack – the sound rising up to its maximum level. If it’s set to nothing, the sound plays at full blast straight away, whereas if you set it quite high then the sound gradually fades (good for string sounds). Decay – this is how long the sound stays at the level the attack brings it up to. If it’s set as high as it will go, it will stay at the maximum level forever (rendering the sustain stage useless). Sustain – this is the level that the sound stays at after the decay...
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Basic Synthesis: Part 2 – Filters

Filters are one of the most important parts of sound creation, and they are a foundation to the whole concept of ‘subtractive’ synthesis. The filters do exactly that – they filter out part of the sound, leaving you with a reduced portion of it, which sounds very different to the whole portion. The main control on any filter is the filter frequency, or ‘cutoff’, which is the key point at which all frequencies are cut off – be it all frequencies which are above, below, in between, or outside of the cutoff point. Common filter types include: Low Pass – the most common type of filter, the low pass allows all frequencies below the cutoff point to pass through. High Pass – the opposite of the low pass filter, the high pass filter allows all frequencies above the cutoff point to pass through. Band Pass – allows a band on frequencies to pass through in the centre, but stops all frequencies outside of...
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Basic Synthesis: Part 1 – Oscillators

Without oscillators, your synthesizer will make no sound (well, actually it can - but that's in a future article). Oscillators produce the original sound which you can hear in your patches, which is then fed through the rest of the signal path in the synthesizer. Oscillation itself is the production of a certain type of waveform, which produces a different sound depending on the shape of the waveform. The waveform is constantly ‘run' depending on the speed/pitch of the note - so if an oscillator is set to a low enough pitch you will eventually hear gaps due to the slow speed of oscillation (see LFO below). Common oscillator waveforms are: Saw Wave - shaped like the teeth on a saw blade, this produces a very common sharp, biting tone. Square Wave - looks like a (near) perfect square, produces a reedy, hollow sound. Pulse Wave - a variation on the above, the pulse wave is half as wide as a square wave,...
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