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What is Chordify?

Chordify is a free online music service – made for and by music enthusiasts – that transforms music from YouTube, Deezer, 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 is a cutting edge service that helps both novice and trained musicians to play the music they want to play, making state-of-the-art music technology available to the public at large.

Technology behind Chordify

We’ve done our best to make our website simple and easy to use, even though there is some complex technology behind Chordify. Our website is built using up to the minute web development techniques, like HTML5 audio etc.

Behind the scenes, we use the sonic annotator for extraction of audio features. More specifically, we extract the NNLS chroma features developed by Matthias Mauch using the Chordino VAMP plugin. These features describe 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 the final transcription. However, where 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 GHCPHPSoXsonic annotator and 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.

The Chordify team

Bas de Haas

After/during his PhD research on music information retrieval, Bas didn’t want his work to get lost in a dusty closet with other PhD theses. He decided his chord recognition algorithm was almost good enough for public use, so he brought together a group of other music enthusiasts to create Chordify.

Dion ten Heggeler

Dion is a communication designer living and working in Groningen. Together with Gijs, he is responsible for Chordify’s design and communication. Dion is dying to learn how to play the guitar.

Gijs Bekenkamp

Gijs is the second half of the Chordify design team. He spent ten years of his life playing in a band with Bas. Alongside Dion, Gijs is responsible for Chordify’s design and communication.

Jeroen Bransen

Jeroen is responsible for the backend of Chordify, and programs mostly in Haskell. Before working at Chordify he obtained his PhD degree in the area of functional programming. Jeroen plays guitar and is a fan of the Dutch band Golden Earring.

José Pedro Magalhães

Pedro worked together with Bas on the core Haskell algorithm behind Chordify during his PhD studies at Utrecht University. Now he lives in London and has an advisory role in Chordify.

Tijmen Ruizendaal

Tijmen plays drums in the band Niek Pronk and DJ HAGY. He’s responsible for the frontend of Chordify and works closely with both the backend guys and the designers.



We would be happy to hear from you. For our most frequently asked questions or suggestions, head over to our UserVoice page.

Chordify offices

Chordify B.V.
Boterdiep 63
9712 LK Groningen
The Netherlands

Utrecht Office
Boothstraat 2A
3512 BW Utrecht
The Netherlands

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Chordify is an online music service - made for and by music enthusiasts - that transforms any song into chords.

Search for any song on Youtube, Soundcloud or Deezer, or paste a link for any of these services.

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