The Naxos Music Library is a service which enables listening to mostly classical music—orchestral and vocal music, operas, etc.—as well as popular, jazz, and ethno music. The service offers over 2,300,000 tracks, equivalent to 150,000 CD-length recordings. In addition to recordings, the service contains brief biographies of composers and artists.
Individual CDs are classified by types of music and detailed categories; you can find recordings in "Advanced search" by one criterion or a combination of criteria including title of CD or track, composer, period, instrument, performing artist, etc.
You are not allowed to download or burn the recordings.