Android's 10 Millisecond Problem Mobile Audio Latency Test App Android Audio Player USB Audio and MIDI for Android

Fastest Mobile Audio Engine for
Games, VR, Music and Interactive Audio Apps

Low Latency Audio. Cross Platform on Android, OSX and iOS. Free.

Echo

echo,delay,beat sync,delay,decayBPM-based Echo for iOS, OSX and Android

Additionally to the traditional decay and dry/wet parameters, the Superpowered Echo features a beat synced twist: the time can be adjusted by bpm-based beats, so you don’t need to manually calculate how many milliseconds to set the delay time.

Most other echo implementations have unnecessarily high CPU usage - but the Superpowered Echo is effectively invisible to the CPU.