modplug doesn't even play some of the most simple IT commands right
Like what?
Some panning commands, excessive abuse of filters, slide-to-note is a bit bugged (IT's slide to note is soundcard dependant, modplug's not), High-value sample offsets get flawed rather often, NNA changing in the middle of a song doesn't always quite work, sample vibratos, excessive abuse of pitch envelopes combined with sustain loops and volume envelope, etc etc etc.
There are tons of these little flaws that sometimes mess up the whole song.
So I wonder, why modplug was hyped as "IT-compatible tracker", as it definetly is not IT-compatible. More like the opposite.
