REAPER is absolutely one of the best pieces of software out there. I’ve been using it too since maybe 2009, though not so much in the last few years (not moved to an alternative, I’m just not doing so much audio these days).

I love the business model, the development cycle, etc. and even though it’s not open source it kinda has a similar community feeling. Every bit as feature-filled and capable as any of the industry standards.

For me it’s Irish traditional music. Aside from having an interesting history, the style often takes a very high level of musicianship to play well. A single monophonic instrument can play a tune and the fast-moving stream of notes can simultaneously spell out melody, counterpoint/call-and-response, and harmony, as well as providing a strong rhythmic pulse (it is music to dance to, after all).