Multimedia is not only about graphics; it is also about sound and music. Applications in this domain are among the most popular in the Android market. Indeed, music has always been a strong engine for mobile devices sales and music lovers are a target of choice. This is why an OS like Android could probably not go far without some musical talent!
When talking about sound on Android, we should distinguish Java from the native world. Indeed, both sides feature completely different APIs: MediaPlayer, SoundPool, AudioTrack, and JetPlayer on one hand, Open SL for Embedded Systems (also abbreviated OpenSL ES) on the other hand: