Using a text-to-speech engine as a musical instrument is so on-topic in my book!

"On-Topic: Anything that good hackers would find interesting. That includes more than hacking and startups. If you had to reduce it to a sentence, the answer might be: anything that gratifies one's intellectual curiosity."

Beatboxing seems to be a very geeky scene. Not that I know much about it, but look at the biggest names in beatboxing - most of them would blend in no problem in any CS department. Looks don't mean much, but still, on interviews these guys give off the same vibe.