Hi!
Are you referring to the AcousticBrainz similarity?
The bad news: We’ve decided to terminate development on the AcousticBrainz project (an announcement is coming soon).
The good news: We’ve worked out a way to calculate recording similarities using the Listen data from ListenBrainz and it is already providing better data than the acoustics based indexes ever did. The very bleeding edge work that is being carried out right now, can be seen here: Dataset hoster: recording-similarity
If you have questions about this data, I would urge you to come to the #metabrainz IRC channel and chat with us. We’d love your feedback and we’d love to see this be used in FW!