音楽：ジャズのスイング感を得るために音符を演奏するタイミングを遅らせる

The swing in jazz music can be enhanced by delaying alternate notes within a bar by 30 milliseconds, reports a study published in Communications Physics. Jazz musicians rated music with a delay to these beats as seven times more likely to have swing compared to musical pieces without delays.

Swing, a term used to describe the feel of musical rhythm, in jazz music is recognised as a key component to the style, but the musical timing behind the phenomena has not been identified. Small deviations or microtimings, are thought to be an important part of creating the swing effect in jazz.

Theo Geisel and colleagues manipulated a segment of music with a soloist section from three songs (The Smudge, Texas Blues and Jordu) to create systematic delays to the ‘downbeats’. Downbeats correspond to the hypothetical strokes of a conductor’s baton (as opposed to the offbeats in between two strokes of the baton). In one condition, the authors delayed the soloist’s downbeats by 30 milliseconds. In another condition, the authors delayed both the downbeats and the offbeats. The authors asked 19 semi-professional and 18 professional jazz musicians to rate the perceived swing in the manipulated music.

When the downbeats were delayed but the offbeats kept the same, the music was 7.48 times more likely to be rated by the jazz musicians as swinging compared to the music without delays. This increased likelihood of a higher rating of the swing in the music was significant. No significant difference was found in music that had delays in both the downbeats and the offbeats compared to the piece without any delays.

The authors show that systematic delays in the downbeats of soloist jazz music significantly increases their swing rating, suggesting that delayed downbeats form a key component of swing in jazz. The authors note that their previous work found that random deviations in the notes did not enhance the swing rating.

Professional jazz musicians gave significantly lower overall swing ratings than semiprofessional musicians, but the authors suggest that this may reflect the higher standards and expectations of professional musicians.

In addition, the authors analyzed more than 450 solo performances of jazz musicians and found such downbeat delays in almost all performances. This suggests that jazz musicians in fact use these subtle timing manipulations in their performances to enhance the swing feel.

The authors conclude that identifying the systematic downbeat delay influence on swing helps more precisely define what swing in jazz music is. They suggest that this understanding could improve computer generated music, which is limited in creating the swing effect in jazz music.