The sale of music for use on mobile phones is already a surprisingly large market, but a European cellular provider sees it almost doubling within five years. The market is currently expected to reach $7.4 billion this year, and Arena Mobile, a Spanish mobile content provider, predicts that that will grow to $13.6 billion in 2011. The sales growth will be driven by Asia, where music and ringtones are especially popular.

Despite the positive news it’s not all sunshine and light for the industry. As revenues have grown telecom operators, content providers and record companies have all been looking for a bigger piece of the pie. That has increased the costs to consumers and decreased profit margins for everyone involved. The key for the industry will be to come up with a revenue model which works and keep innovating to find new ways to make their offerings simpler and more attractive to consumers.