Streaming music service Pandora has revealed that its mobile apps have now been installed by more than 13 million iPhone, BlackBerry, Palm and Android users.

Nine million of those were new accounts being created from the smartphones, as opposed to existing Pandora users going mobile, CTO Tom Conrad tells GigaOm.

That means nearly a quarter of Pandora's 38 million users discovered the service through their mobile handset, rather than the web.

Meanwhile, Conrad claims that currently, half of all new signups to Pandora are coming from the mobile apps; and that a quarter of the music streamed through the service is to handsets.

These stats show why Pandora and its rivals - Spotify's iPhone and Android apps launched earlier this Summer - see mobile as key to their strategy going forward.