loop_tune support

[michael02022]

This opcode works (so far) in Dimension Pro, while in sforzando is ignored.
It works as an additive to the tune opcode of the sample. For example, if my tune is -15, and my loop is tuned at -20, then I should write loop_tune=-5 to make it work as intended.

loop_tune is a feature that early samplers/romplers had. And for a good reason.
This feature let you make a one cycle loop and fix the tune of the loop. This is essential for any sample that has continuous waveforms and let you extend the
decay of it without modifying/processing the sample data.
So you can make different map variants of the same sample, and it saves a lot of time for cases where you just want to extend the decay of a sampled instrument since you don't need to process and re-save the same sample, avoiding bloats to the sample set.

Here a very simple demo of the opcode: loop_tune demo.zip