While most of the traditional music industry was in Los Angeles for the Grammys, nearly 200 hackers were crowded into New York start-up space General Assembly, spending the weekend hunched over laptops while trying to build the next great music tech product. After a round of demos from companies like Soundcloud and the Echo Nest, the mostly male, mostly twenty- and thirty-something hackers set to work, sprawling on sofas and congregating in conference rooms, tossing around ideas before hunkering down over their laptops. Many of the sponsor-companies provided APIs for the hackers to build on, and almost all ended their presentations with a mention of the fact they were hiring developers.

(Check out our report from Hack Day at MIDEM last month.)

The hackers did take a break for pizza - appropriately, there were about a hundred cheese pies with a number of sauces so each person to customize their slice - and later in the evening for a dance party with DJ/Rupture. Some of the more hardcore folks stayed all night, although not all of them worked through it - at one point, there were several young men curled up on the couch taking power naps.

On the afternoon of the second day, presentations commenced - 72 hacks had been uploaded to the Music Hack Day wiki, and each had two minutes to present. While the time limits proved too difficult for some - a multi-user call-in karaoke app ran out of time halfway through - the rapid fire presentations all had a few things in common: they were creative, and many were actually practical. Some, like Stringer (a virtual string instrument drawn in the air that's played using the Kinect, by one or more people) had real educational value; it could perhaps be used to teach kids without access to instruments about the fundamentals of music. Others, like Tweets on Beats (which sets a tweet to a beat) and Rhyme My Tweet (which matches a tweet with a rhyming pop lyric) would surely be favorites of Kanye West. Some people built hacks that created personalized Valentine's Day playlists, and one, White Limo Dedicator, actually allowed users to send a new Foo Fighters track with a dedication to that special someone.

Several sponsors gave individual prizes, and the Hack Day handed out three at the end, which were voted on by the crowd. Third prize ($1,000) went to Stringer (see above); second prize ($3,000) went to djtxt, which allows users to text song suggestions and build a crowd-sourced playlist; and first place ($5,000) went to Tim Soo, who created an invisible violin.

Head here for a list and links to the hacks, and check out the tweets at @billboardbiz and @cortneyharding, and look for much more Music Hack Day coverage in Billboard magazine in the coming weeks.