I had to carefully watch the peak meter several times before I finally noticed what the hell you were talking about But yes, I definitely see the little peak now and I know what is causing it.
Let’s say you have a sample with no instrument envelope. The sample is playing and then you have a note-off command to stop it. The sample doesn’t immediately go from full volume to dead silence - this would cause a horrible click in almost every instance. So instead there is a very quick volume fade out to give a cleaner note-off.
To demonstrate things, I’m using a pulse sample which goes immediately from dead silence to 50% volume and then stays at 50% volume (basically creating pure DC offset which is very useful for highlighting strange behaviour, or to see the exact effects of a volume envelope, etc).
A note-on followed by a note-off looks something like this:
You can see very clearly that the sample started correctly, with no volume ramping occuring, but at the note-off there was some volume ramping down to silence.
Now let’s look at turning the sample on and off using volume commands:
Here we can see that Renoise is now ramping the volume up as well as down. Again, this is simply to avoid nasty clicks that would normally occur from instant volume changes.
Finally let’s look at a note-on, followed by a 2nd note-on, then a note-off:
This one is quite interesting. I’ve highlighted in dark red where the first note-off is fading out to silence. We can clearly see that while this first note is fading out, the tail is actually mixing back into the beginning of the 2nd note and causing a brief spike due to their combined volume. This is what seems to be happening to your breakbeat sample.
So… what can you do about it? Well, unfortunately I don’t think you can really do much to stop this since it is simply a part of the audio engine. And to be honest, the benefits from this behaviour are probably far more important than the side-effects. Quick volume changes and note-off’s without this feature would sound a lot more noisy and nasty.
Something you could try is to add a volume envelope with sustain to the breakbeat, and immediately before you play a new note (with sample offset or something) add a note-off command. Of course this might affect the sound of the break too much, giving it a more stuttering feeling with all the little fade outs from the envelopes, and you might need to double the resolution of your song to get enough accuracy with the note-off positions…
However… looking into this problem gave me an idea which could possibly be useful in a future update to Renoise. Maybe it would be possible to enable/disable this volume ramping per instrument or sample, if the user is absolutely certain that they don’t need it?
Taktik… any thoughts?