Napster rolled out a new Web service, which offered fans the chance to listen to more than 2 million tracks for free, a Reuters report said.
The report said the new service was supported by advertising and followed months of negotiations with record companies.
Napster would split advertising revenue with the record companies based on the number of times one of their artists' songs was played, the report said.
The new service, which was added to Napster's existing subscription service, also allowed users to send direct links of chosen tracks to friends, the report said.
Users could listen to songs up to five times on the free site before having to pay, the report added.
The report further said the online firm expected the free service to increase visits to the site, which had been selling music downloads and had seen about 2 million visitors a month.