Chordify is a free online music service – made for and by music enthusiasts – that transforms music, from YouTube, SoundCloud or your private collection, into chords. Our service automatically recognises chords from the audio signal, and aligns them to the music in a simple and intuitive player. Chordify makes state-of-the-art music technology available to a broader audience, making it easier and more fun to play along with your favourite tracks.
From Blog | Chordify | Tune Into Chords http://chordify.net/pages/.
See video with Bas de Haas, January 11, 2013, at Eurosonic Noorderslag at http://youtu.be/9s2ZGbRoleM .
An application of a Ph.D. dissertation by W. B. de Haas on “Music Information Retrieval Based on Tonal Harmony” at http://igitur-archive.library.uu.nl/dissertations/2012-0217-200249/UUindex.html .
How do they do it?
Technology behind Chordify
We’ve made our best to make our website look simple and easy to use, even though there is some complex technology behind Chordify. Our website is built with state-of-the-art web development techniques, like HTML5 audio etc.
Behind the scenes, we use the sonic annotator for extraction of audio features. These features consist of the downbeat positions and the tonal content of a piece of music. Next, a Haskell program HarmTrace then takes these features and computes the chords. For this to happen HarmTrace uses a model of Western tonal harmony to aid in the chord selection. At beat positions where the audio matches a particular chord well, this chord is used in final transcription. However, in case there is uncertainty about the sounding chords at a specific position in the song, the HarmTrace harmony model will select the correct chords based on the rules of tonal harmony.
Chordify fosters open-source software. Not only do we use open-source software packages like GHC, PHP, SoX, sonic annotator, MongoDB, but we also give back a large share of the in-house developed technology to the music information retrieval research community via open-source software projects like HarmTrace and scientific publications.
Chordify could not have been realised without the support of Utrecht University.
From “How to Use Chordify” at http://chordify.net/pages/how-to-use-chordify/