Transpose a song

To transpose is to move every note up or down by the same distance. Sheet music is transposed by rewriting it; a recording is transposed by shifting its pitch while keeping its timing, so the song plays in the new key at the same tempo and length. AudioRinse does it in your browser, and shows the key the song moves to.

Played faster, a record also plays higher; slowed down, it plays lower. AudioRinse keeps the two apart with Signalsmith Stretch, an open-source pitch and time-stretching library made for music with many instruments at once. It cuts the sound into short overlapping slices, moves each slice's frequencies or its timing, and joins them back up, here in your browser.

You hear every change as the song plays, and the download is made the same way, faster than real time. On test tones every pitch we checked, from an octave down to an octave up, landed within 2 cents of the target, and every speed gave exactly the expected length.

Seven semitones up reaches the same key as five down, so a song never needs to move more than six either way. Small moves sound the most natural; past three or four semitones, voices start to sound noticeably higher or deeper.

• Singers bringing a song into their range for practice, an audition or a performance.
• Guitarists playing along without a capo: if the recording uses a capo on the 3rd fret, transpose it down 3 semitones and play the same shapes open.
• Worship and cover bands rehearsing a song in the key they'll play it in.
• Players matching a recording to a chart written in another key.