Category Archives: music

computer science math music

Audio Fingerprinting

The first time I saw the Shazam app, I was floored. The app listens to a clip of music through your phone’s microphone, and after a few seconds it is able to identify the recording. True to its name, the software works like magic. Even with significant background noise (for instance, in a noisy bar) the app can recognize that Feels Like We Only Go Backwards is playing on the jukebox.

I recently came across a fantastic writeup by Will Drevo about how “audio fingerprinting” schemes are able to correctly identify a recording. Will wrote an open source Python library called dejavu for audio fingerprinting. His writeup gives a detailed overview of how the software works. Will’s explanation is a gem of expository writing about a technical subject. He gives an overview of the requisite knowledge of signal processing necessary to understand how the fingerprinting works, then describes the scheme itself in some detail. Essentially the software works in four steps:

  1. Build a spectrogram of a recording.
  2. Find “peaks” in the spectrogram.
  3. Identify patterns or “constellations” among the peaks which will serve as fingerprints for the recording.
  4. Apply a hash function to the fingerprints to compress them to a more reasonable size.

Will’s explanation of how and why these steps work to give a robust way of recognizing audio recordings is vivid and accessible. It is a remarkable narrative about how signal processing, optimization, and data structures combine to create a truly miraculous product.

music musings

Revel in Ravel’s Repetition

Bolero has been stuck in my head for the past couple days.

You can download a recording of Bolero here. Bolero was one of Maurice Ravel’s last compositions, and is of a very different nature from his earlier work. This Radiolab podcast postulates that Ravel suffered from frontotemporal dementia. The podcast draws a parallel between the end of Ravel’s life, and the life of biologist-turned-painter Anne Adams. See some of her paintings here.


Girl Talk: The Culmination of 50 Years of Popular Music

The first time I heard Girl Talk (wikipedia), I wasn’t immediately enamored with his music. I first listened to his Night Ripper several years ago, and while I didn’t dislike it, I wrote it off as a novelty. I thought it was just a series of mashups somewhat inconsistently stitched together. More recently, however, I listened to his latest album, All Day (which incidentally is freely available for download here). Then I listened to the album again. And again. I was instantly drawn to its more refined character. While ostensibly it is a mashup album, its 71 minutes weave a seamless tapestry depicting Girl Talk’s vision of the last 50 years of popular music. An interesting problem would be to identify every sample on any given track.

The vocals on most tracks are taken from hip-hop songs, as rapping lends itself well to the mashup genre. The musical accompaniment runs the gamut of the last half century of popular music: Missy Elliot raps over the Ramones and Daft Punk, Jay-Z over Modern English and General Public, Lil Kim over The Jackson Five, Ol’ Dirty Bastard over Radiohead, The Beastie Boys over Iggy Pop, to name a few examples. On listening to All Day, it is interesting to me how Girl Talk’s clever juxtapositions completely change my impression of the lyrics. The re-contextualized vocal samples highlight the absurdity of some aspects of the rhetoric in hip-hop. Ultimately, though, the album is playful, light-hearted and often hilarious. Plus it is great to dance to.


Isabella Stewart Gardner Museum Music Archive

I’m always looking for classical music recordings in the public domain. While there are a ton of recordings posted on various archives around the internet, I have yet to find a single authoritative place to look for free classical music online. I recently came across the music archive of the Isabella Stewart Gardner Museum in Boston. The site contains recordings of over 150 concerts performed at the museum, all free to download. You can browse by performer, composer, genre and period which is quite handy. Recordings of entire concerts are also available as a podcast which includes brief comments about the history and context of the pieces performed. The archive is far from authoritative, but it contains a growing collection of high quality recordings in a easily browsable format.