I submitted my Acid Machine site in 2015, it's a web based synth and drum machine app. I didn't expect much to happen, just wanted to get a bit of feedback. It ended up featuring on a few high profile music sites and for the next week it got 70,000 users a day. I didn't post it anywhere else so it all originated from HN in some way.
Since then I have released version 2 which has the ability to add fx to the instruments, use MIDI devices and lots more. It gets a few sales a week with traffic still coming from those music sites.