Mobile music is any audio file that is played on a mobile phone. Mobile music is normally formatted as an AAC (Advanced Audio Coding) file or an MP3, and comes in several different formats. Monophonic ringtones were the earliest form of ringtone, and played one tone at a time. This was improved upon with polyphonic ringtones, which played several tones at the same time so a more convincing melody could be created. The next step was to play clips of actual songs, which were dubbed Realtones. These are preferred by record labels as this evolution of the ringtone has allowed them to gain a cut of lucurative ringtone market. In short Realtones generate royalties for record labels (the master recording owners) as well as publishers (the writers), however, when Monophonic or Polyphonic ringtones are sold only publishing or "mechanical" royalties are incurred as no master recording has been exploited.^[6] Some companies promote covertones, which are ringtones that are recorded by cover bands to sound like a famous song. Recently Ringback tones have become available, which are played to the person calling the owner of the ringback tone. Voicetones are ringtones that play someone talking or shouting rather than music, and there are various of ringtones of natural and everyday sounds. Realtones are the most popular form of ringtones. As an example, they captures 76.4% of the US ringtone market in the second quarter of 2006, followed by monophonic and polyphonic ringtones at 12% and ringback tones and 11.5% – but monophonic and polyphonic ringtones are falling in popularity while ringback tones are growing.^[7] This trend is common around the globe. A recent innovation is the singtone, whereby "the user’s voice is recorded singing to a popular music track and then “tuned-up” automatically to sound good. This can then be downloaded as a ringtone or sent to another user’s mobile phone" said the director of Synchro Arts, the developers.

As well as mobile music there are full track downloads, which are an entire song encoded to play on a mobile phone. These can be purchased and bought over the mobile network, but data charges can make this prohibitive.^[8] The other way to get a song onto a mobile phone is by "side loading" it, which normally involves downloading the song onto a computer and then transferring it to the mobile phone via Bluetooth, infra-red or cable connections. It is possible to use a full track as a ringtone.

Mobile music is becoming an integral part of the music industry as a whole. In 2005 the International Federation of Phonographic Industries (IFPI) said it expects mobile music to generate more revenues that online music before the end of that year.^[9] In the first half of 2005 the digital music market grew enough to offset the fall in the traditional music market – without including the sale of ringtones, which still makes up the majority of mobile music sales around the globe.^[10]