# Accelerate for synths

**URL:** <https://uzu.lurk.org/t/accelerate-for-synths/4889>\
**Category:** TidalCycles\
**Tags:** questions\
**Created:** [19 September 2023 19:15 UTC](https://uzu.lurk.org/t/accelerate-for-synths/4889 "2023-09-19T19:15:27Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![julian](https://uzu.lurk.org/user_avatar/uzu.lurk.org/julian/32/1398_2.png) [@julian](https://uzu.lurk.org/u/julian)\
**Post date:** [19 September 2023 19:15 UTC](https://uzu.lurk.org/t/accelerate-for-synths/4889/1 "2023-09-19T19:15:27Z")

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Forever, there has been a bug in superdirt that made accelerate not work properly. I am posting this here, because fixing it may change how synths sound – so please chime in.

There is an issue here: [Set DirtFreqScale default factor to 1 by wimmers · Pull Request #280 · musikinformatik/SuperDirt · GitHub](https://github.com/musikinformatik/SuperDirt/pull/280)

Let's list what the correct behaviour should be.

- speedFreq: 0 –\> output: 1
- speedFreq: 1, accelerate: 0 -\> output: speed
- speedFreq: 1, accelerate: 1 -\> output: speed ... rising to over sustain time to (speed \* 2)
- speedFreq: 1, accelerate: -1 -\> output: speed ... falling to over sustain time to 0
- speedFreq: 1, accelerate: 0.5 -\> output: speed ... rising to over sustain time to (speed \* 1.5)
- speedFreq: 1, accelerate: -0.5 -\> output: speed ... falling to over sustain time to (speed \* 0.5)

We have `(speed * (accelerate + 1))` as an end speed.

All in all, this should sound like in samples.

There, we also have: `endSpeed = speed * (1.0 + accelerate);`

Now, two questions:

- are the above what you'd expect?
- are you sure that we should make the synth freqs depend on speed for everyone? Originally I thought that synths should not behave like samples in every way, i.e. when you set a note or a freq, you may expect that to be the way it is.

Needless to say that acceleration should work!

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**Author:** ![Jeff\_Brown](https://uzu.lurk.org/user_avatar/uzu.lurk.org/jeff_brown/32/2033_2.png) [@Jeff\_Brown](https://uzu.lurk.org/u/Jeff_Brown)\
**Post date:** [2 October 2023 12:27 UTC](https://uzu.lurk.org/t/accelerate-for-synths/4889/2 "2023-10-02T12:27:04Z")

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Seems right to me!

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**Author:** ![julian](https://uzu.lurk.org/user_avatar/uzu.lurk.org/julian/32/1398_2.png) [@julian](https://uzu.lurk.org/u/julian)\
**Post date:** [15 October 2023 13:51 UTC](https://uzu.lurk.org/t/accelerate-for-synths/4889/3 "2023-10-15T13:51:16Z")

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Ok, so this is merged – I hope it'll be as expected for everyone …