I wonder what was the first track to be sold through Internet (and when / under what circumstances it took place).
According to http://inventors.about.com/od/mstartinventions/a/MPThree.htm the first label which sold mp3s was SubPop.
1989 - Fraunhofer received a German patent for MP3.
1992 - Fraunhofer's and Dieter Seitzers audio coding algorithm was integrated into MPEG-1.
1993 - MPEG-1 standard published.
1994 - MPEG-2 developed and published a year later.
November 26, 1996 - United States patent issued for MP3.
September 1998 - Fraunhofer started to enforce their patent rights. All developers of MP3 encoders or rippers and decoders/players now have to pay a licensing fee to Fraunhofer.
February 1999 - A record company called SubPop is the first to distribute music tracks in the MP3 format.
1999 - Portable MP3 players appear.
It all started in Fall 1993, when a Santa Cruz, Calif.-based outfit, Internet Underground Music Archive, or IUMA, created an FTP site where people from all over the world could download music files via the Internet. To reduce audio files to a manageable size, IUMA compressed them with MPEG and made a free decoder available for downloading.
Source:minidisc --> check Music Meets The Web
There is also reference of this on Wikipedia
The Internet Underground Music Archive (IUMA) was an organization that provided a venue for unsigned artists to share their music and communicate with their audience. IUMA's goal was to help independent artists use the Internet to distribute their music to fans while circumventing the usual distribution model of using a record company. IUMA was started by Rob Lord, Jeff Patterson and Jon Luini from the University of California, Santa Cruz in 1993.[