Melodyne

Melodyne, made by Celemony, detects the notes in a recording and shows each one as a shape on a piano-roll grid. You can drag a note to correct its pitch, change its timing or length, or adjust how much it wavers, while the sound stays natural. Its Direct Note Access feature reaches individual notes inside polyphonic audio, so you can fix one note in a strummed guitar chord or a piano part.

Bands mostly use it to tune vocals and tighten timing after recording, and it is also a useful way to see exactly what was played, which helps when transcribing. It runs as a standalone program and as a plugin inside most recording software, where ARA support lets it work directly on the tracks in your session. It is detection and editing software you drive by hand, so how natural the result sounds depends on how far you push it.