It would surprise many to know that while sales of music CDs are well on the way down, the sales of cellular ringtones are going stronger than ever. Worldwide,  cellular ringtones  produced a turnover of 5 billion USD as of 2006, with the revenue expected to continue rising for a few years. What has started out as a simple way of letting you know when your phone is being ringed up is now an industry worth billions, with no end clearly in sight for the spectacular growth being expected. It will be interesting to see how events will play out with this technology.