Jazz musician Louis Armstrong, shown holding a trumpet, recorded “What Is This Thing Called Swing?” in 1939. Science may now have an answer.

Haywood Magee/Hulton Archive/Getty Images

It don’t mean a thing if it ain’t got that swing — all you’ve got to do is stagger your timing.

For decades, fans of jazz music have debated why some songs have swing — the characteristic swaying feeling that compels feet to tap and heads to bop. Now, scientists may finally have an answer to Louis Armstrong’s classic song “What Is This Thing Called Swing?” and the secret lies in the timing of jazz soloists.

Headlines and summaries of the latest Science News articles, delivered to your inbox

Thank you for signing up!

There was a problem signing you up.

After listening to original and digitally tweaked piano recordings, jazz musicians were more than seven times as likely to rate music as “swinging” when the soloist’s timing was partially delayed with respect to the rhythm section, researchers report October 6 in Communications Physics.

In jazz, musicians are trained to swing eighth notes, or extend the duration of their downbeats — every other eighth note — and shorten the beats in between to create a galloping rhythm. But the technique on its own doesn’t explain swing, says physicist Theo Geisel. Computer-generated jazz songs with swung eighth notes still lack the style’s swaying feel ( SN: 2/17/22 ).

Past research hinted that swing might arise from differences in the timing between musicians within a band ( SN: 1/2/18 ). So Geisel and colleagues tweaked only the timing of the soloists in jazz recordings on a computer and asked professional and semiprofessional jazz musicians to rate each recording’s swing.

Musicians were nearly 7.5 times as likely to judge music as more swinging when the soloists’ downbeats were minutely delayed with respect to the rhythm section, but not their offbeats.

In a new study, jazz musicians rated the “swing” of these recordings of the song “Jordu” by Clifford Brown. The first recording is an unaltered version, and the second recording has been manipulated to increase the delay of the soloist’s downbeats by a very small amount. The musicians rated the tweaked recording as having more swing than the original.

Most of the musicians couldn’t put their finger on what was causing the effect, says Geisel, of the Max Planck Institute for Dynamics and Self-Organization in Göttingen, Germany. “Professional jazz musicians who have played for many years apparently have learned to do this unconsciously.”

The researchers also analyzed 456 jazz performances from various artists and found almost all soloists used downbeat delays, with an average delay of 30 milliseconds. This average held across the jazz subgenres of bebop, swing and hardbop, though there was some variation, Geisel says. “For faster tempos, the delays get smaller.”

Looking ahead, Geisel intends to investigate how “laid-back playing” — a popular style of delaying both downbeats and offbeats in jazz — influences swing.

C. Nelias et al. Downbeat delays are a key component of swing in jazz . Communications Physics. Vol. 5, October 6, 2022. doi: 10.1038/s42005-022-00995-z.

Nikk Ogasa is a staff writer who focuses on the physical sciences for Science News . He has a master’s degree in geology from McGill University, and a master’s degree in science communication from the University of California, Santa Cruz.

Science News was founded in 1921 as an independent, nonprofit source of accurate information on the latest news of science, medicine and technology. Today, our mission remains the same: to empower people to evaluate the news and the world around them. It is published by the Society for Science, a nonprofit 501(c)(3) membership organization dedicated to public engagement in scientific research and education (EIN 53-0196483).

Subscribers, enter your e-mail address for full access to the Science News archives and digital editions.

Not a subscriber?
Become one now .

Here’s where jazz gets its swing