Following libraries with help you create apps which are related to sound and music, be it music player or sound recording apps.
Noise is an Android wrapper for Kiss FFT, a small mixed radix FFT library that can use either fixed or floating point data types.
WaveFileGenerator is a small library used for generating a .wav file in main directory for a given frequency.
This is one of the most robust Android Audio recording library. It supports RxJava but not fully.
JcPlayer is a simple audio player library for Android. You can get audio playback working quickly by using a simple view, JcPlayerView. All settings and controls are created by the player view. It support sound files from asset and raw folder and even from an external URL.
AndroidAudioRecorder is a fancy audio recorder which supports WAV format at 48kHz.
This is an Android library to shape a voice with an instrument.
As the name states, it is a playlist file (*.pls) parser library for Android.
Soundify library makes the transformation and transmission of certain information into sound waves.
The library can help make an Android app that convert audio files. It support many sound formats, including AAC, MP3, M4A, WMA, WAV and FLAC.
Track Searcher can be used to retrieve full information about music track by its title. It gets track data from parsing of data from iTunes, SoundCloud, and last.fm.