Caller tune is a feature that allows a mobile phone user to personalize the music or sound that a caller hears while waiting for the call to be answered. It is different from a ringtone, which is the sound that a phone makes when receiving a call. Caller tunes are a chargeable service and can be set up by subscribing to a monthly service or purchasing credits to use for the service. The service has grown in popularity in emerging markets such as Africa, Bangladesh, and particularly in India. Caller tunes can be personalized by selecting a song or sound effect from a library of available options. Some caller tune services also allow users to record and upload their own audio message or song. The use of caller tunes has enabled many artists to add an extra revenue stream by receiving royalties when their songs are used as caller tunes.