This bug has actually 2 problems in one, and since they're related, I'm going to put them in one topic.
Full Version:
OpenMPT v1.17.045
Description of the bug:
It began when I wanted to make an instrument for my VSTi. Made a new sample (empty one) and made an associated instrument. Added the vsti and everything was good.
At a later stage, I added a normal instrument with samples. Since my earlier sample was seen as empty, it somehow was seen as unused even though an instrument has this number assigned to it. (bug 1) As result, my vsti started to also play this sample when I play it. I could manually add an empty sample but I figured, what If I enter 0 as sample? 0 seems to add a .. like unconfigured. The right mouse button then says: replace all with sample 0, so I did that. At this point, the VSTi refuses to make any sound, but the rest of the song still works. My question there for is: can sample 0 be seen as an empty sample?
How often does it happen?:
Always
How to reproduce (step by step description):
BUG1: Make a new song, add a sample and say yes to the question to associate it to an instrument. Go to the instrument tab, and add another instrument. Drag in an instrument that uses samples, and notice how instrument 1 (with the empty sample) suddenly starts to make a sound.
BUG2: make a new instrument, assign a VSTi to it, enter 000 as sample so it says sample: .. and then rightclick and choose: set all to sample 0. Notice how you can't get any sound out of it at all until you enter a number. Its even so that if you have all but one have a normal number and that one has .. then 2 notes won't produce sound anymore.
I was able to reproduce BUG1 only when using some song cleanup before adding the instrument with samples; was this the case for you too?
No, I can make it happen instantly, just make sure the instrument says ... by entering three 0's.
I encountered this while working on a song and that song didn't had a cleanup. Made a few tests and this was a way to reproduce it.
EDIT: oops, thats bug2 :P
I have to check about 1, but I have encountered this combination of bugs while editing a song without doing a cleanup, so its possible to get to it without a cleanup.