My basic analogue string model has some similarities to the computer one but the version above, uses standard analog synthesiser functions with the special delay line module.

First the sound of a pick is needed.
White noise and a fixed voltage source are fed into a mixer module and then into an envelope shaper. The controls are adjusted to produce a very short burst of noise; (all frequencies) along with a transient voltage step (kick). This is a simple model of the sound energy produced the moment you pick. (The shorter the noise burst the ‘thinner’ the pick). This pick energy is fed into the delay line module . It’s the looped delay feedback that models the actual string. The delay just simply represents the time it takes for a vibrating string to vibrate through one cycle. For a 100Hz bass note, this would be 10 mlliseconds (1/100 of a second). The important feedback loop setting round the delay controls the amount of noise energy burst that gets cycled round the delay loop (‘string’ sustain). The nearer feedback is set to unity gain the longer the sound goes round and round the loop before dying away.
The noise burst also takes a certain time to complete each delay loop. Noise frequency components progressively get organised; quickly favouring those that fit this loop time nicely. Those that fit nicely sustain well and those that don’t, quickly die away as they get averaged out.
Also, since all ‘string’ overtone frequencies fit perfectly to multiples of the loop time, they also sustain well. This causes a harmonically rich pitched note of a period the same as the delay time to be created out of the noise pulse. This is the string resonance effect. You can hear this working in the first part of the string sound example on the next page. First you hear just a repeated noise burst: the pick on it’s own. Then the delay feedback is increased and the loop starts to ring. You can still hear the noise at the start and the organised pitched note being created from it. It sounds electronic yet acoustic too and it’s a really nice sound, but maybe just a little electronic?

String developement....

There is a softness and a give with most real strings due to the materials they are made from. By introducing the delay line’s inbuilt mild low pass filter or equaliser into the resonant loop, the high frequency gain is reduced and consequently higher harmonics will die away around the loop quicker than lower ones. The lower the frequency the filter is set, the ‘softer’ will be the material the string is made of. Additionally, the string tension is increased a bit when a string is plucked, after which it quickly returns to normal as the sound dies away.
In the string sound example mentioned above, after the ringing is established, you can hear the delay module's filter being slowly closed making the sound softer more like a nylon string. Next the tension is given a blip at the start of the note by the extra circuitry that modifies (blips) the keyboard voltage control source.

A fully developed string model patch is shown below incorporating all of the above components plus the addition of a simple body described on the next page..

Fully developed string patch with added body resonator.

How the plucked string model works....

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My basic analogue string model has some similarities to the computer one but the version above, uses standard analog synthesiser functions with the special delay line module.

First the sound of a pick is needed.
White noise and a fixed voltage source are fed into a mixer module and then into an envelope shaper. The controls are adjusted to produce a very short burst of noise; (all frequencies) along with a transient voltage step (kick). This is a simple model of the sound energy produced the moment you pick. (The shorter the noise burst the ‘thinner’ the pick). This pick energy is fed into the delay line module . It’s the looped delay feedback that models the actual string. The delay just simply represents the time it takes for a vibrating string to vibrate through one cycle. For a 100Hz bass note, this would be 10 mlliseconds (1/100 of a second). The important feedback loop setting round the delay controls the amount of noise energy burst that gets cycled round the delay loop (‘string’ sustain). The nearer feedback is set to unity gain the longer the sound goes round and round the loop before dying away.
The noise burst also takes a certain time to complete each delay loop. Noise frequency components progressively get organised; quickly favouring those that fit this loop time nicely. Those that fit nicely sustain well and those that don’t, quickly die away as they get averaged out.
Also, since all ‘string’ overtone frequencies fit perfectly to multiples of the loop time, they also sustain well. This causes a harmonically rich pitched note of a period the same as the delay time to be created out of the noise pulse. This is the string resonance effect. You can hear this working in the first part of the string sound example on the next page. First you hear just a repeated noise burst: the pick on it’s own. Then the delay feedback is increased and the loop starts to ring. You can still hear the noise at the start and the organised pitched note being created from it. It sounds electronic yet acoustic too and it’s a really nice sound, but maybe just a little electronic?

String developement....

There is a softness and a give with most real strings due to the materials they are made from. By introducing the delay line’s inbuilt mild low pass filter or equaliser into the resonant loop, the high frequency gain is reduced and consequently higher harmonics will die away around the loop quicker than lower ones. The lower the frequency the filter is set, the ‘softer’ will be the material the string is made of. Additionally, the string tension is increased a bit when a string is plucked, after which it quickly returns to normal as the sound dies away.
In the string sound example mentioned above, after the ringing is established, you can hear the delay module's filter being slowly closed making the sound softer more like a nylon string. Next the tension is given a blip at the start of the note by the extra circuitry that modifies (blips) the keyboard voltage control source.

A fully developed string model patch is shown below incorporating all of the above components plus the addition of a simple body described on the next page..

Fully developed string patch with added body resonator.

How the plucked string model works....

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