Ableton Live is a music production app for writing, producing and performing music. Live 12 adds new ways to generate and reshape MIDI ideas and to find the right sounds.

Key features:

Reshape MIDI clips with Transformations such as strums, ornaments and acceleration curves.
Generate melodies, chords and rhythms with MIDI Generators.
Stay in a chosen scale with Keys and Scales, or work in tuning systems beyond 12-tone equal temperament.
Design sounds with the Meld synthesizer, Roar saturation and Granulator III.
Find similar sounds and swap Drum Rack samples with Sound Similarity Search.
Use the Mixer in Arrangement View and stack Clip and Device views to see more at once.

Live 12.4 is a free update for Live 12 users and adds Link Audio.