Why am I seeing "Trackable" in my server logs?

Trackable is the name for Chartable's analytics prefix.

Trackable fetches MP3s for analysis, collecting file size, ID3 tags, and other information required for Chartable’s IAB-compliant statistics. Files will be fetched from different IPs in the Amazon EC2 ranges.

Though we strive to reduce the load on your servers, it’s possible a file will get fetched multiple times.