Subject: Article: The Science of Swing
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All that Jazz

It don't mean a thing if it ain't got that swing. But what is

WHEN the musical West Side Story opened in London in 1958 the
producers had a real problem. They didn't know who should occupy
the drum stool. Leonard Bernstein's score was hard. And it was
jazzy. At the time most of Britain's jazz drummers wouldn't do
because they simply couldn't read music well enough. The
classical percussionists, though flawless readers, also had an
irredeemable failing. These "straight" musicians, as the jazz
world calls them, just couldn't swing.

Swing is at the heart of jazz. It's what makes the difference
between music you can't resist tapping your feet to and a tune
that leaves you unmoved. Only now are scientists beginning to
unravel the subtle secrets of swing. Even today, many drum
instruction manuals lay down a rigid formula for swing, based on
alternately lengthening and shortening certain notes according to
a strict ratio, says Anders Friberg, a physicist at the Royal
Institute of Technology in Stockholm, who's also a pianist. But
these rules are misleading. "If you took them literally you would
never learn to swing," says Friberg.

The fundamental rhythmic unit in jazz is the quarter note. When
you tap your feet to the music you are marking out quarter
notes--or crotchets as they are called in Britain. Superimposed
on this basic beat are melodies. Often melody lines consist of
eighth notes, which last half as long on average as a quarter

But no one plays music exactly as it is written, just as no two
people would read a passage from a book the same way. If you want
to hear music played exactly as written there are thousands of
Midi files on the Net which are direct translations of sheet
music. And very tedious they are too--convincing proof that
computers don't have a soul. Real musicians shorten one note,
lengthen another, delay a third and accent notes. It is all part
of creating an individual style.

In jazz this interpretation is taken to extremes--and the way
jazz musicians play their eighth notes is one of the keys to
swing. Faced with a row of eighth notes on a sheet of music a
straight musician plays a series of more or less equal notes. A
jazz musician plays the eighth notes alternately long and short.
The long note coincides with the basic beat, the note clipped
short is off the beat. There is a similar but less pronounced
tendency to play notes long and short in folk and baroque music
as well as in popular music.

Many drum instruction books say that the long eighth note should
be twice as long as the short one. But you simply can't lay down
a rigid formula for swing, says Friberg. It all depends on the
tempo of the piece you are playing. Although professional
musicians are largely aware of these complexities--or can at
least feel how to swing--inexperienced musicians may not be so
lucky. Friberg points out that many contemporary rock drummers
may pick up bad habits because they practise keeping time by
playing with drum machines, which may rely on the simplistic
swing formula.

Friberg measured the ratio between the long and short notes, the
swing ratio, of four drummers on a series of commercial
recordings. They included some of the best drummers in jazz, such
as Tony Williams who played with Miles Davis on the My Funny
Valentine album, Jack DeJohnette, part of Keith Jarrett's trio
and Jeff Watts, who played with Wynton Marsalis.

Friberg used a frequency analysis program to pick out the
distinctive audio signal of the drummer's ride cymbal from a
series of 10-second samples from the records. In modern jazz,
drummers normally play a pattern of quarter notes and eighth
notes on this cymbal with their right hand. He found the drummers
varied their swing ratio according to the tempo of the piece. At
slow tempos the long eighth notes were played extremely long and
the short notes clipped so short that they were virtually
sixteenth notes. But at faster tempos the eighth notes were
practically even. The received wisdom of a 2 to 1 swing ratio was
only true at a medium-fast tempo of about 200 quarter-note beats
per minute. "The swing ratio has a more or less linear
relationship with tempo," says Friberg.

Although this relationship between the swing ratio and tempo held
true for every drummer, there were some notable stylistic
differences. "Tony Williams, for example, has the longest swing
ratios," says Friberg. This is partly his style. But jazz is also
a cooperative style of music--you have to fit in with those
around you. "It's partly a matter of who he is playing with,"
says Friberg.

Friberg backed up his findings by creating a computer-generated
version of a jazz trio playing the Yardbird Suite, a theme
written by Charlie Parker. He then played the piece back to a
panel of 34 people at different tempos and asked them to adjust
the swing ratio. He found that the listeners also preferred
larger swing ratios at slow tempos while at fast tempos the ratio
was closer to 1.

The results are impressively consistent--and they also give a
clue to the split-second accuracy that jazz musicians have to
achieve if they are going to keep the listeners tapping their
feet. At a relatively slow tempo of 120 beats per minute most
listeners prefer a swing ratio somewhere between 2.3 and 2.6.

Meaure for measure: for a swinging performance, the first of each
pair of eigth notes is played longer than the second. The melody
line also hangs behind the cymbal beat, except for occasional
off-the-beat synchronisation, which keeps the band together.

Part of the reason for this relationship between the swing ratio
and tempo, says Friberg, may be that there is a limit to how fast
musicians can play a note--and how easily listeners can
distinguish individual notes. At medium tempos and above, the
duration of the short eighth notes remained more or less constant
at slightly under one-tenth of a second. The shortest melody
notes in jazz have a similar minimum duration. Friberg thinks
this should set a maximum practical tempo for jazz of around 320
beats per minute, and very few jazz recordings approach this

He points out that there's a limit to the speed listeners can
process notes. When the tenor saxophonist John Coltrane made his
first solo recordings in the late 1950s jazz critics began
referring to his fast succession of notes as "sheets of sound".
"This is what you hear if you don't hear the individual notes,"
says Friberg.

Just as jazz musicians have a standard repertoire of tunes, so
there is a similar repertoire of jokes. One has a member of the
audience asking: "How late does the band play?" to which the
answer is: "About half a beat behind the drummer." That joke
turns out to have more than a grain of truth in it.

In his latest research, Friberg went back to the same recordings
and looked at the timing of soloists, such as Miles Davis, to see
if they used the same swing ratios as the drummers. He found that
the soloists' swing ratios also dropped as the tempo increased.
More surprising was the fact that the drummer always played
larger swing ratios than the soloist they were playing with. Even
at slow tempos soloists rarely had swing ratios greater than 2 to

The difference helps to explain why a soloist can seem to be so
laid back on a particularly toe-tapping number. When playing a
note that nominally coincides with the basic quarter-note beat,
the soloist hangs back slightly. "The delay can be as much as 100
milliseconds at medium tempo," says Friberg.

This tendency to hang behind the beat goes back to the musical
ancestors of jazz. In the introduction to the 1867 book Slave
Songs of the United States Charles Ware, one of the editors,
observed that when they were rowing a boat, the oars laid down
the basic beat for the slaves' singing. "One noticeable thing
about their boat songs was that they seemed often to be sung just
a trifle behind time," he said.

Members of the audience synchronise with the band by tapping
their feet to the basic beat. But musicians have a more subtle
strategy. "If you generate a solo line with a computer and delay
every note relative to the cymbal it sounds awful," says Friberg.
"The funny thing," he adds, "is that there is a distinctive
pattern that most musicians are not aware of. They synchronise on
the short eighth note."

He says that this off-the-beat synchronisation of the soloist and
the rhythm section is crucial in keeping the band from falling
apart. Effectively the musicians synchronise their internal
clocks every few beats throughout the piece. When the
off-the-beat notes are synchronised, says Friberg, "you often
don't realise the soloist is lagging".

So how did the producers of West Side Story resolve their
drumming dilemma? Even after 42 years musicians still tell the
story. At the time Britain's best jazz drummer was Phil Seaman,
who was a good reader. But he had a problem. Or to be precise,
two problems. One was alcohol and the other heroin. But after
some dithering, the producers gave him the job. All went well
until one matinee, when the regular conductor took the day off.

Seaman had a habit, half-affected, half-genuine, of appearing to
doze when he wasn't playing--and during one pause in the music,
his head began to nod. Fearing that he had dropped off and wary
of his reputation, the conductor gestured frantically to the bass
player to wake the dozing drummer. The bass player reached across
and prodded Seaman with his bow. Startled, Seaman stood up and
fell backwards over his drum stool, straight into the Chinese
gong--which reverberated around the theatre and stopped the show.

Seaman stood up, cleared his throat, and announced: "Ladies and
gentlemen, dinner is served." The management promptly sacked him.

Mick Hamer

From New Scientist magazine, 23 December 2000.