This feature is intended to be a convenience for users as well as a
way of bringing (minute) revenues to the project: setting search fall-
through to include Amazon or other online music retailers, while at
the same time creating an affiliate account with them. Amazon exposes
many of its features via an SOAP-based API, and PHP implementations
exist for this (see
http://www.amazon.com/gp/aws/sdk/103-3161897-3233408? for details).