Applications of audio-based similarity still seem rather rare nowadays. Once in a while a startup claims that they're using it for recommendations, but looking at their results might suggest that they are just using metadata instead (for example, see
this example which Paul recently blogged about).
Anyway, here is an example where 100% pure audio-similarity is being used:
FM4 soundpark. The feature launched today. For anyone who doesn't read German: soundpark is the number one place for new Austrian artists to expose themselves online. Soundpark has been around for ages. Long before Myspace or similar sites became popular. Soundpark has a devoted community and is well integrated into one of the most popular radio stations in Austria (the FM4 station which reaches out to younger demographics favoring alternative/indie music).
However, attention is usually only paid to new releases and old ones can get buried quickly. To help users navigate and find content researchers from the legendary
OFAI (including
Martin Gasser and
Arthur Flexer) in collaboration with
Gerhard Widmer's department of computational perception (including
Dominik Schnitzer) have helped FM4 integrate audio-similarity into their system. There is a bit more information on OFAI's page
here and some more information in German can be found on
orf.at.
To each song on Soundpark users will get 3 acoustically similar songs, and there seems to be a feature that allows creating a playlist by defining a starting and end song (but I haven't found that feature yet).
Soundpark hosts about 5000 artists with each a few tracks in average. (If I'm not mistaken they got about 8800 tracks.) They are constantly growing. According to the press releases they have a number of plans to add additional features to make it easier to navigate their content and discover interesting artists. Great news! Makes me especially happy knowing that it's former colleagues who are building this.
