Maybe the one thing missing would be time stretch.
Play Store info:
Androsynth is a full featured multi-track audio composer, audio editor and effect creator. It contains an audio editor which you can use to import audio files, add effects to them and slice them in samples, an effect editor that allows you to create your own effects from elementary blocks, and a tracker that you can use to compose new music using those samples and effects.Some features are limited in the demo version: songs are limited in duration and there is a maximum number of elements you can use to create effects. There is no limitation in the sampler.
Sampler features :
► Import most audio file formats including MP3, Vorbis, FLAC, WAV, even audio tracks from videos
► Record audio from the internal microphone
► Add effects such as pitch change, low pass filter, wah-wah, etc ...
► Convenient zooming and editing features
► Save as sample
► Unlimited number of tracks
► Individual mute/solo/volume control for each track
► Expand and repeat samples
► Add effects and filters independently to each voice
► Master song as WAV in CD quality (44.1kHz, 16bits, stereo)
► Save/load project
► Zooming, panning, full multitouch support
Effect editor features :
► Create your own audio filter effects
► Start from a preset library of effects that you can modify
► Use your effects anywhere in the application
※ For optimal use it is recommended to use this application with tablets or phones with a 4.7inch or larger screen.
There is more tutorials on the Youtube channel and on the official website: