Up to 20% of mobile users are listening to music on their mobile. That's the findings of the latest M:Metrics report (via SMS Text News). This sits very nicely with the numbers Nokia have reported for sage of their Music Store - 20% of eligible users have registered with the store. Nokia also report that 25% of that number (ie 5% of the total) use the on-device client; a significant improvement on the 1.1% that M:Metrics report downloading direct to the device.

Of course that number is for mobile phones globally, and most modern mobiles can play MP3 in some format (even a mono MP3 ring-tone probably qualifies for this survey), so that's not a complete 1 to 1 comparison. I'd be interested in seeing a breakdown on a per device basis and see if the music based handsets do have a x5 improvement over the regular handsets.

"Mobile music is quickly catching on, and the fact that consumers are sharing music demonstrates its potential as a social, viral phenomenon centered on mobile handsets," said Jen Wu, analyst, M:Metrics. "The proliferation of musicphones is causing a shift in digital music toward the mobile platform, which opens numerous opportunities for music-related content, services, hardware and accessories built to accommodate or enhance these mobile music activities."

The report and stats are here.