Sales of music-playing mobile phones hit half a billion units in 2007, outnumbering shipments of personal media players like the iPod by almost 300 million, according to MultiMedia Intelligence. The analyst anticipates that in 2011, over half of all mobile phones will be considered music phones with 941 million units shipped.

"Voice commoditisation and falling voice call prices are driving a shift in wireless operators to focus on data revenue models and services," said Frank Dickson, chief research officer for the firm.

"Music has been the first 'killer app' for the operators to drive the consumption of premium content on the handset," he explained.

See also:

Apple iPhone review