Part hackathon, part music tech gathering, Music Hackdayis an event where participants conceptualize, create and present/demo their music applications all in one weekend. As Music Hackday Boston concludes this afternoon, I've listed their creative projects below - almost 40, which is extraordinary considering they had less than 48 hours, so congrats to everyone - you guys did some great work!

• Paul's Music Wreckommender: an anti-recommender. Give it an artist that you like and it will return a list of artists that are as far away as possible form the original (project page).
• Remix Shell: a simple command shell for Echo Nest Remix one-liners (project page)
• Fugueomatic: Fugues are pieces of music that follow a certain set of rules and a number of voices come in, like a "round", and end up in somewhat different places than where they start out, all the while following a fairly strict and established form (project page)
• EchnoNestLive: EchoNestLive let's producers sample songs in ways they never have before. Using EchoNest's APIs to analyze songs and using Java, Max/MSP, Ableton Live and MaxForLive to play back pieces of a song based on specified pitches, loudness levels, timbres, and other parameters (project page).
• MySpace Hacked V1.0: a user friendly MySpace design/template, that supports the new 360 environment (project page).
• Bricolage v10e-6: The EchoNest Remix API includes functionality to break down a song into short units of sound [segments], and also to measure features on these segments [pitch classes, timbre, and volume are currently provided].  Previous work by Ben Lacker [afromb.py in the echonest remix examples directory] resynthesized a track by mixing in closely matching segments from a different track (project page)
• LastFMD2FWTFBBQ: hacked LastFM and the Topspin applications to show offers from an artist inside the LastFM buy button drop-down menus (project page)
• Playdar SoundCloud resolver: resolves SoundCloud search results for Playdar (project page)
• SoundCloud Paulcast: enables podcasts for SoundCloud resources, both private and public.(project page).
• Noteflight Audio-to-Notation Import: a hack of the Noteflight web-based notation editor to import free-range MP3s on the web into a rough "skeleton" of a musical score, using the EchoNest Remix API to supply a metrical and key signature analysis and some rough notions of pitch and harmony.  The resulting score, when played, follows the score in metrical synchronization with the original audio track (project page).
• Melody Search with Noteflight API hack: a hack to use NoteFlight's embeddable Score Objects to let users pick out specific pieces of a melody to search a large database of scores for similar songs (project page).
• HTML5 <audio annotation: a jQuery plugin that uses the HTML5 media elements API to show elements at certain timestamps during the playback of audio or video media (project page).
• Location-aware Blog-aware Contextual Concerts Listing: create an upcoming concerts listing, specific to the users location, but based off the posting history of a music blog. In essence, highly relevant upcoming concerts (project page).
• Ambient Text Mashup of "HashMap" & "Frequency" for Modest Mouse: The Good Times Are Killing Me: ambient Text Mashup of "HashMap" & "Frequency" for Modest Mouse: The Good Times Are Killing Me (project page).
• MixApp Live Acts Mashup: given an existing social music listening application, add a pane which displays upcoming shows for the artist currently playing, and a link to buy tickets.  Integrate the buy function into the live chat. (project page)
• Sonar: a front-end to control your Sonos multi-room music system that allows you to scan your friends Twitter, Last.FM or other (to be implemented) feeds for music recommendations. We then use Playdar to resolve those songs to playable tracks, and enqueue that music for playing anywhere in your house on your Sonos system. (project page)
• Sonos-Twitter Rewriting: artist, album, and track metadata are conveniently supplied to the Sonos-Twitter service, but they are currently being ignored by the official service.  This hack takes advantage of the metadata and adds rewrite rules which can be shortened in many convenient ways (project page).
• Audio to Midi to Score: using the EchoNest API for audio analysis in conjunction with spectral imaging tools, it's a prototyped audio-to-midi conversion.  The resulting midi file can be played or imported into NoteFlight (project page).
• Amazon EC2 image for music mashup sites: an amazon EC2 image for easy bootstrapping of music- and audio-heavy websites (project page)
• iTunesAirBridge and Playdar AS3 Lib: This project demonstrates using the NativeProcess API to access iTunes via Windows COM.  The demo only contains two commands for retrieving the user's library and playlist.  However, because the iTunes interaction happens via VBScript on Windows (and soon AppleScript on OSX) so anyone can easily extend the library to do more (ie creating playlists, writing a download manager for a music store that imports to itunes) and not have to deal with compiling and scripting C (project page)
• Music-Synchronized Composing Interface Using Echonest API: musicpainter is a collaborative graphical composing environment created by Wu-Hsi where novice users can easily create and share music (project page).
• Outlier FM: Outlier FM is a weekend's attempt to utilize advanced technology to search for beauty and surprise in even the most overproduced of popular music (project page). 
• PartyLister: the PartyLister is a playlist generator built to try out new collaborative playlist generation ideas (project page).
• playdarTunes: playdarTunes allows you to play your iTunes music inside the browser using Playdar. It will open and parse an iTunes Music Library XML file. The music can then be played from a local disk or anywhere Playdar resolves it to (project page) 
• Large-scale similarity using EchoNest: looking at usual patterns in a subspace of the EchoNest dataset made out of 43K songs (project page).
• Cowbot: used the Echo Nest Remix API to extract beat timings, then fed these timings to a servo that plays the cowbell in time with any song (project page).
• Bandsintown City Mixtape: mixtape of artists playing shows in a given city, links to buy tickets through Bandsintown. (project page). 
• Bowie S-S-S-Similarities: I used the Musically Intelligent Machines autotagging api to analyze and tag all of David Bowie's music.  Then I lined it up in order and calculated the similarity between every 10-second clip and every other 10-second clip in terms of the automatically generated descriptions.(project page). 
• Lyric Similator: Lyric Similator lets you explore songs based on the similarity of their lyrics (project page). 
• NPR Tourfilter Mashup: adding NPR stories about music artists to tourfilter's drop-down metadata section for concert listings (project page). 
• Quasiphone: The Quasiphone is a new instrument which uses musical notation in the browser as the controller (project page). 
• DJ Hot Scene: DJ Hot Scene is a hack that pulls MetaData from Native Intruments Tracktor Scratch Pro DJ Tool. The current artist and song is extracted through a faux icecast server (project page).
• Hammond Organ Hacking: Hammond organ "chopping" is an industry unto itself (making large and heavy organs into manageable and modular pieces (project page).
• JamTones on Android: (project page).
• SoundCloud Phanai iPhone App: (project page).
• Living Playlist: The Living Playlist is a real-time, collaborative playlisting web app to encourage social listening through the web (project page).
• Napster Playdar Resolver: Napsdar uses the Napster API to provide access to Napster's streaming collection via Playdar (project page).

This looks like such a good time that I'm gonna try and bring it to Atlanta and Georgia Tech's Center for Music Technology.