Les Paul layers guitar parts by re-recording each pass on top of the last, on a modified tape deck. Every part is fused to the others, and one mistake means starting again.

Ampex delivers a custom eight-track recorder to Paul, soon nicknamed the Octopus. Each part now has its own track and can be redone without touching the rest.

The Beatles spend about 700 studio hours on the album, most of them at Abbey Road, on four-track machines. Full tracks are bounced down together to make room, fusing those instruments on the master.

Guitar Hero ships with each song's guitar on a track of its own: miss a note and the guitar drops out of the mix until you hit the next one. Rock Band does the same for drums, bass and vocals in 2007, and a whole generation hears what a record sounds like with one player missing.

The Beatles: Rock Band is built from the band's master recordings, with Giles Martin producing the music. The early songs were cut on two- and four-track tape with several instruments sharing a track, so his team had to separate them with digital filters at Abbey Road.

Deezer releases Spleeter and Facebook's research lab publishes Demucs, both free: programs that take a finished recording and return the vocals, the drums, the bass and everything else as separate audio.

The record billed as the last Beatles song is finished after machine separation lifts John Lennon's voice off the piano on a home demo from the late 1970s, something the band had tried and failed to do in 1995.

Tempo and feel. The drums tell you how fast the song is, whether it swings or drives, and often the era of the production. Britannica's dictionary defines the rhythm section as the part of a band that plays the rhythm, typically the drums and the bass.

The harmony arrives. A bassline walks through the roots of the chords, so with two parts playing you can hear where the song goes as well as how it moves.

Guitars, keys, synths, strings, horns. This is where the riff or the hook usually lives, and where the genre stops being a guess: a piano ballad, a guitar band and a synth record cannot be mistaken for each other.

The giveaway. In a 2021 study at the University of Oldenburg, listeners picking one part out of a two-second mix found the lead vocal more reliably than the bass, drums, piano or synthesizer. The voice is what ears lock onto, which is why it comes last.

Hal Blaine opens the Ronettes' record with a four-beat phrase he later said began as a missed beat. The Recording Academy calls it one of the most widely imitated beats in rock and pop, and lists 30 later songs that use it.

Gregory Coleman plays alone for four bars, six or seven seconds, in the Winstons' Amen, Brother. By 2015 it had been counted in 1,862 other recordings, which the BBC called one of the most sampled pieces of music in history.

Clyde Stubblefield's 20-second break on the James Brown single has been sampled in more than a thousand songs. Rolling Stone's obituary called him the most sampled drummer in hip-hop history.

Tap along before you think about titles. Fast or slow, straight or swung, four on the floor or a backbeat: tempo and feel cut the field down further than any single sound does.

Once the bass is in, hum the first tune that fits over it. The bassline fixes the chords, the chords limit the melodies, and the right one often turns up on its own.

Say the instruments out loud: acoustic guitar, electric piano, a string section, a drum machine. The line-up dates a record and places its genre before a note of the tune is clear.

A run of Layered is 5 songs. Notice which parts helped you name each one, then try another run with that in mind. The next set is one press away.