The topics for the rounds for the 2015 (2nd) NGMT are as follows:
Round 1: Percussive. You may only use one-shot instruments, percussive instruments, plucks, etc. And no, no cheesing out with spiccato or heavy reverb - as in, no using reverb to make a sustained note out of a one-shot, and no using short bursts of notes with sustain - if it can be sustained, it's out.
Fun fact - the first round has already had similar issues to the first round last time - defining the limits is much easier said than... stated.
Round 2: Soundfont. You may only use soundfont players (so no resampling) and the Fluid GM bank. Beyond that, you can have your normal effect library - but no other instrument channels beyond the Fluid bank in a soundfont player. So it's like raw midi, but with slightly higher quality instruments and FX channels.
Fun fact - it took quite awhile to pick a good GM bank. It's also the GM bank I used when I first started making music!
Round 3: Inspired! No challenge here. Use whatever tools you have!
The only theme to always be round 3! Always.