Microtiming Studies (rhythmic feel), Swing Rhythm

[Jazz+]

Full article : Microtiming Studies

EXCERPT:

"I have experienced one of the most interesting musical revelations of my life, gradually over the last several years, in studying West African dance-drumming and in playing jazz, hip-hop and funk. The revelation was that the simplest repetitive musical patterns could be imbued with a universe of expression. I have often witnessed the Ghanaian percussionist and teacher C. K. Ladzekpo stopping the music to chide his students for playing their parts with no emotion. One might wonder how much emotion one can convey on a single drum whose pitch range, timbral range, and discrete rhythmic delineations are so narrow, when the only two elements at one's disposal are intensity and timing. Yet I have become convinced that a great deal can be conveyed with just those two elements. Some investigations into how this can happen are set forth in this chapter."

 

"In groove-based music, this steady pulse is the chief structural element, and it may be articulated in a complex, indirect fashion. In groove contexts, musicians display a heightened, seemingly microscopic sensitivity to musical timing (on the order of a few milliseconds). They are able to evoke different kinds of rhythmic qualities, such as apparent accents or emotional mood, by playing notes slightly late or early relative to their theoretical metric location."

[Jazz+]

All That Jazz

New Scientist vol 168 issue 2270 - 23 December 2000, page 48

 

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

 

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 notesor 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 note.

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 tooconvincing 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 extremesand 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 complexitiesor can at least feel how to swinginexperienced 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 musicyou 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 consistentand 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.

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 noteand 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 speed.

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 1.

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".

 

 

How the written and played music differ

 

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 playingand 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 gongwhich 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.

[Jazz+]

[video:youtube]

 

Thelonious Monk plays "I'm Confessin'." [CD-49] One of the most fascinating skills displayed by Monk and many other pianists of the genre is a high degree of independence between the two hands, to the degree that one hand can appear to perform rhythms that are ambiguously if at all related to those performed by the other. Often, as in stride piano, this takes the form of a steady pulse or repetitive bass rhythm in the left hand (the "ground"), and upper-register, rhythmically free melodies in the right hand (the "figure"). A classic example is Monk's 1963 solo recording of "I'm Confessin' (That I Love You)" (Monk 1998). In this piece, after carrying on in this expressive stride fashion for some time, the last two bars of the first chorus give rise to an improvised melodic fragment that rhythmically seems to stretch and tumble into the next bar [CD-50].

 

 

 

In this excerpt, the melodic structure in the right hand temporarily overrides and upsets the underlying rhythmic structure, only to be righted again. We can interpret Monk's unquestionably gripping display here as the rhythmic equivalent of a struggle, one that threatens the norm of established pulse regularity set by what has come before. It seems to offer an example of a case in which such regularity is sacrificed briefly to allow for a case of extreme rhythmic expression. But note that the sense of pulse is never lost; Monk leaves out a couple of quarter-note chords in the left hand, but otherwise provides strong and accurate pulse reinforcement in the stride style. The rhythmic underpinning of the left hand compensates for the apparent deviation from regularity.

 

When I played the recording of this piece for a roomful of cognitive science undergraduates, most of whom presumably had no familiarity with jazz, this excerpt elicited a burst of spontaneous laughter. Something about Monk's delivery is communicative enough to transcend what one might expect of the traditional confines of genre. Nearly upsetting the regular pulse, Monk takes a chance and chooses to follow through on a melodic idea that momentarily takes him rhythmically far afield.

 

The question of whether Monk "intended" to play this in exactly this way is a pejorative one, akin to reifying the role of "mistakes" in jazz (as in Walser 1995). From the perspective of an improvisor, the notion of a mistake is supplanted by the concept of displaying one's interaction with the structure suggested by the sonic environment. It is never clear what is "supposed" to happen in improvised music, so it makes no sense to talk about mistakes. This improvisation-friendly framework allows for the possibility of musical exploration and experimentation, including impromptu rhythmic variation of the sort described here, without invoking a notion of mistakes

[Jazz+]

[video:youtube]

 

Ahmad Jamal plays "But Not for Me." [CD-51] A wonderfully extemporaneous, playful spirit is captured masterfully in pianist Ahmad Jamal's 1952 trio version of the standard tune "But Not for Me." In this piece, Jamal manipulates his relationship to the pulse actively and voluntarily through the skillful use of microtiming variation. Nearly every single phrase in Jamal's rendition contains some interesting microrhythmic manipulations, but here I will focus on one fragment, namely the end of the first chorus into the beginning of the second chorus. In measure 31, Jamal initiates a repeating three-beat figure in the four-beat metric context. This additive rhythmic technique is a common one in African-American music, and Jamal carries it out to a humorous extreme, letting the blues-inflected figure cycle twelve full times (nine measures). The first four measures of this passage are displayed below. I have adhered to the convention of representing swung rhythms with regular eighth notes, but it should be understood that there is much more to this passage than meets the eye. In particular, Jamal plays this figure extremely behind the beat, so much so as to enhance the humorous effect of the repeating melodic figure by casting it in starker relief against the more ordinary rhythmic background [CD-52].

 

 

 

In these four measures, the quarter note averages 469 milliseconds (128 beats per minute). The note events in the piano that are displayed as occurring on the beat tend to begin actually around 40% of a beat later than the drummer's rimshots, which are indicated with x's above. This places him more than a triplet behind the beat. Furthermore, Jamal's second eighth note in each swung pair tends to occur about 85% of the way through the beat. This means that the swing ratio here is effectively inverted; the first eighth note in a delayed pair lasts about 45% of a beat (less than half), and the second lasts about 55% (more than half). It would appear that the perception of swing arises due to complex variations in timing, intensity, or articulation; in this case, it is not merely a matter of achieving the "correct" microrhythmic ratio.

 

How does Jamal pull off this apparent rhythmic violation of an inverted swing? The answer seems to lie in his 40% phase shift relative to the beat established by the accompanying instruments. If, while maintaining this phase relationship, he were to adhere to the usual swing ratio of around 57%, then the second note in a swung pair would be close enough to the onset of the next beat (only a few percent early) that it would be heard as on-the-beat. By employing a relative anticipation of the second eighth note in each pair, Jamal avoids this problem, instead sounding squarely "between" the beats. The 40% delay also affords him enough rhythmic ambiguity so that the inverted swing does not sound jarring. Also, Jamal enhances the sense of swing by accenting the second of each pair (a common technique, as mentioned earlier). So here is a case in which one kind of rhythmic expression interacts with another; the usual long-short relationship of swing is altered in order to accommodate the "laid-back" quality of the melodic figure.

 

What is accomplished by playing in this laid-back, behind-the-beat fashion? One might expect the same simple perceptual effects (such as enhancing stream segregation) if he instead played ahead of the beat, for example. Playing behind the beat is definitely a cultural aesthetic in African-American music, especially jazz. In an unpublished study, Bilmes (1996) found that a West African drummer played equally as often ahead of as behind the beat, whereas one might observe casually that skilled jazz improvisors tend to play much more often behind than ahead. From the ecological point of view, playing behind the beat might be normally associated with a physical or mental state of relaxation, or might suggest a causal relationship in which the musical material is a reaction to the pulse. Such hypotheses would demand further investigation.

 

In this chapter I have discussed some aspects of rhythmic expression that are quite distinct from the common body of European classical musical performance techniques typically discussed. Instead of (or in addition to) expressive concepts like rubato, ritardando, and accelerando, we have seen deliberately asynchronous unisons, subtle separation of rapid consecutive notes, asymmetric subdivisions of a pulse, and microscopic delays. As further illustration, we have seen extremely deft manipulation of fine-scale rhythmic material in examples from the jazz idiom. I have chosen to focus on African and African-American musics because they often feature these concepts in isolation from the possible interference of tempo variation, and because they tend to involve percussive timbres which facilitate precise microrhythmic analysis. I have argued that African and African-American musics incorporate aesthetics that value these kinds of microrhythmic expression. However, I believe that these techniques are found to varying degrees in all music, including the European classical genres. In the next chapter, I present a representation for rhythmic structure that allows for the explicit manipulation of expressive microtiming of the variety discussed above.

[16251]

I will focus on one fragment, namely the end of the first chorus into the beginning of the second chorus. In measure 31, Jamal initiates a repeating three-beat figure in the four-beat metric context. This additive rhythmic technique is a common one in African-American music, and Jamal carries it out to a humorous extreme, letting the blues-inflected figure cycle twelve full times (nine measures).

The timing during that lick and how Ahmad gets out of it, is something I've listened to a zillion times. It's very audience friendly, love it.

[Theo Verelst]

Great music.

 

Another interesting thought might be that certain as you call it "micro-" rhythmic variations, when repeated consistently turn into very recognizable style figures I think. Depends on the accuracy and clarity of the repetition to get recognized as a style instead of an error.

 

Monk of course does more than micro-rhythmic things, mainly he plays around the "sound" that the timing of chords and notes in the chord will create, and make a swing or something else out of components that the listener will hear come together (if they're a bit experienced, otherwise it will be subconscious or possibly the perception will not say much about what the piece actually does) during the course of the song.

 

T.

[stoken6]

Just after I read this thread, Herbie's Cantaloupe Island came on the radio. There's something going on with that groove which I can't make out. It has that loping/lopsided, slightly unbalanced quality which I can detect, but I can't rationalise it.

 

Any insights? I'm not sure if the basic pulse is offset slightly on certain beats, or whether it's as a result of certain instruments playing ahead/behind.

 

Cheers, Mike.