When is this mobile music business really going to take off? Not any time soon, a new Jupiter research report reckons. Just five percent of US mobile subscribers sideload tunes from their computer while less than half of that, two percent, download tracks over the air, despite the steady emergence of this model with online stores from Nokia (NYSE: NOK), Jamba and MusicStation.

The most common practice, rather prosaicly, is assigning ringtones to phone book contacts (16 percent), even ahead of over-the-air ringtone downloads (12 percent). The sticking points? In this order - price, discovery, UI, DRM, storage and the fact many mobile users already use other portable music players.

There’s no great compulsion from users either. Two thirds said nothing would motivate them to listen to music on a mobile. The top motivator - guaranteeing tracks are $0.99 or less. Just 14 percent of users want over-the-air tunes. All the numbers jump for the 18-to-24 bracket but the outlook is still glum. Jupiter: “Absent some exciting new business models, music labels and carriers will continue to cede most of the digital-music turf to Apple.” The survey polled 1,815 US adults.