Los Angeles-based Napster said today that the firm's music subscription service is now available on all of NTT DoCoMo's handsets. The firm said that its over-the-air (OTA) service is now available across DoCoMo's complete line of handsets. Napster originally announced plans to deploy its service with the Japanese telecommunications firm in April; the firm's mobile services in Japan are a joint venture with Tower Records Japan and NTT DoCoMo. The new service will be billed directly through subscriber mobile phone bills. Napster is a provider of a digital music subscription service. The firm also provides its mobile music subscription service through au/KDDI, and has offered its PC-based music subscription services in Japan since last year.