Buffer: random start position

Questions
2

That’s a simple typo :smiley: !

You didn’t specify the startPos flag argument, so, currently, your startPos variable is passed as trigger:

This should be:
sig = PlayBuf.ar(2, buf, BufRateScale.kr(buf) * rate, startPos: startPos, loop: 0);
or
sig = PlayBuf.ar(2, buf, BufRateScale.kr(buf) * rate, 0, startPos, loop: 0);

As a side note, even if it does not impact your algorithm, I’d advocate using z[\buffer] and z[\bufferPlayer] instead of z.buffer and z.bufferplayer (see this post about this syntax distinction).