Currently (checked at 16 Aug 2011) the most challenging module category BotB has to offer, most likely because the average (read: not Strobe) .xm fanboy would make crap for a 4K and die attempting a 2K.

Having said that...

To measure what sort of stuff can be made for an 8K module, we'll take a look at the two categories below it (which aren't BotB categories yet): 4KB and 2KB. This is mostly based on iamgreaser's opinion.

When aiming for a tiny module, it will often be less than 4KB, but ever so slightly greater than 2KB after having the utter crap beat out of it. Without turning your piece into a smouldering pile of crap, 2KB is the lower bound. This also seems to apply to demo coding.

8KB is actually quite challenging to fill properly without resorting to flooding the module with samples, unless you're making a .mod, in which case you'll have a hard time finding any space when each pattern is 1KB.

Or if you don't know your pattern packing and decide to make a 24 channel .xm which when resaved as an .it goes down to about half the size. michu, take note.

Or if you're using buttplug and you manage to flood the crap out of your file with MIDI info. ant1, take note.

Or if you're using quite a few instruments in instrument mode in .it and not munching. I cant think of anyone who's done this.

Whatever.

Rule number one (for any size compo for that matter) is KNOW YOUR FORMAT. .s3m and .it work well with (at least horizontally) sparse patterns, whereas .xm really only works when the patterns are quite dense, and .mod isn't packed so it's advised that you suck every ounce of pattern you can. .it also has the added bonus of being able to reuse previous values (note, ins, vol, eff type + param (essentially a 2-byte field)) and so it can actually be very good if you use a crapton of channels for notes at different volumes / pitches / whatevers.

Rule number two is learn how to reuse patterns well. .it has per-channel volumes. For those of you who don't know where F1 is on your keyboard (read: .xm users), you may need to exploit the fact that in s3xmodit, playing a note without defining an instrument will play the note without resetting the volume to the sample default (note: for .mod it apparently doesn't retrigger the note either, but most players don't follow this behaviour so be wary). With that said, E6x/SBx (loop x times) can be useful. Also, don't be afraid to abuse your orderlist, especially if you can change your pattern lengths.