Next steps: XM

MOD playback is not nearly good yet (especially because a lot of effects aren't implemented or correctly working yet), nevertheless I am going to implement the other file loaders first, to establish a common, internal structure of the loaded module.
Actually, after MOD I wanted to implement S3M loading, then XM, then IT. However, I am not very sure about the S3M format, but I already quite understand the XM format, so I decided to prefer the XM format. I think, XM is much more used as S3M is, and propably many XM formats, that don't have any special effects, would be playable quite soon after the implementation of the loader.

XM introduces one relevant feature, that was missing in MOD files: instruments. Whereas MOD only had pure samples, which I could play directly in the MOD player (except for volume, panning etc. from the pattern descriptions), I need at least another node on top of it, representing the envelope of the instrument. Fortunately, the parameters of various nodes (such as the gain of the GainNode) support linear transitions from one value to another value, so I am not in need to update the volume/panning values at each possible time offset in between of two envelope points. However, I need to implement this feature and selecting the sample depending on the requested note.

I think, I should get the basics of XM working this week.