# [music-dsp] Reading a buffer at variable speed

```I am having trouble with this concept for quite some time now, I hope that
I can explain it well enough so you can understand what I mean.
I have signal stored in a buffer of known length. The buffer must be read
at a variable speed, and the variations in speed have to be exponential, so
that the resulting glissandi are (aurally) linear. In order to do that I
came up with the following formula:```
```
x[t] = t * sample_rate * end_speed^(x[t] / T)     where T is the total
length of the buffer in samples.

This doesn’t seem to work and I can’t understand why.

And my second question is, how can I get the resulting length in
milliseconds? (how long will it take to play the whole buffer)

I hope I managed to be clear enough!

Maxi

--
Maximiliano Estudies
+49 176 36784771
maxiestudies.com
```
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