Hey guys!
I am trying to stretch a loop to use in a song. I tried using various pitch shifting ladspa plugins, like rubberband and AM pitchshifter, but no matter how much or how so small I change the loop, it will not be flawless. The original tempo of the loop is 130, the tempo of the song is 129. If I set the tempo of the song to 130, the loop is perfect.
Using rubberband I tried adjusting cents, since a semitone is too much down, but going even 0.5 cents down instantly produces very noticable artifacts and there is always a noticable artifact in the end of the loop. I mean - I hear the change in the pitch, but I do not hear the change in the length of the loop.

I tried doing auto stretching in QTractor, thinking I just cannot find the correct value, but in QTractor the result is the same - there is a noticable gap(artifact) in the end which makes the loop not perfect.

Also, as soon as rubberband plugin is activated - the loop goes out of sync with the rest of the song even if I make no changes - there appears a slight pause before the loops starts to play. No such effect with AM pitchshifter.

Eventually, what I did was change the pitch of the loop 15 cents down by means of the Pitch knob in the lmms instrument window. It worked, although did tune it down a bit, but hardly noticable. Of course, I would prefer to stretch a sample without shifting its pitch.

So I have two questions.

1. Am I doing something wrong with Rubberband or is it really not that top notch?
2. How much cents is 1 bpm?


ps: tried elastique stretching of the same sample in FL Studio. Although nice result I did hear some slight artifacts.