Shifting Gears on Mystic Brew and Human Nature

(Update November 7th 2022 When during fall I started my second year of South-Indian Rhythm studies at the Conservatory of Amsterdam I came to realize that my speed analogies are off the mark. The rhytmic device illustrated in this post would be better explained by refering to a tala change. The term speed¹ is used for the Anuloma-Pratiloma technique. I’ll leave the following post as it is for now in order to save my car and boat analogies - devices I, by the way, absolutely don’t care about - and to track my progress.)

Steady as she goes◊

Vijay Iyer’s cover versions of Mystic Brew and Human Nature use the same techniques to create a sense of urgency and acceleration while still keeping a very relaxed groove.

Mystic Brew starts out as a regular $\frac{4}{4}$ or $8$ quavers, then moves to $13$ beats, then $21$ beats and back to $8$ beats. Human Nature starts in $\frac{13}{8}$ and shifts gears from there. These three divisions of Mystic Brew are played two times over while the two divisions in Human Nature are played in sequence only once. I’m using the word gears because it is closely related to the term speed to be differentiated from tempo.

This sequence $8,13,21$ can be found in the Fibonacci sequence. In 2009 Iyer wrote an article² for the The Guardian illustrating the rhythmic foundation of Mystic Brew. He uses the Fibonacci sequence $0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, …$ where each number is the sum of the two preceding ones and each ratio of two consecutive numbers tends to the golden ratio as $n$ increases ($3/2=1.5$), ($5/3=1.6666$), etc. etching closer towards $1.618033…$

“In our version of Mystic Brew, we work with that asymmetry and move it through Fibonacci-like transformations."²

The mathematics are certainly interesting but not enough to unlock some of the mysteries of this performance. I pieced together informations from different sources³ including private lessons with the Vijay Iyer trio bass player Stephan Crump.

There is also some guess work involved. One one hand no transcription or analysis can do justice to the actual performances. On the other if Vijay Iyer himslef writes about his music in a major newspaper there might be value in exploring some of the underlying musical principles.

The math behind all of this is “only” the initial spark. The musicians are performing at a deep level of perception and interaction. The drummer Marcus Gilmore: “When people ask me what the music sounds like, I just say, ‘I play free.’”⁴ Iyer wrote his Ph.D. dissertation about embodied cognition.⁵ Bassist Stephan Crump says:

“For me it’s booty first, then the hearth, then the mind."⁶

The rest of us though will have to first get our … up the mountain in order to admire the view.

A Ronnie Foster classic◊

Mystic Brew original is a 3 bar tune shown here in Iyer’s transposed version:

“The three beats and five beats of the original are transformed to a faster five beats and eight beats (totalling 13), which then becomes a still-faster eight beats and 13 beats (totaling 21). Each transformed measure is roughly the same length and, importantly, the second chord lands at roughly the same time, about 3/8 of the way through (or 5/13, or 8/21)."²

The harmonic rhythm with the two chords per bar placement will stay the same but with a slightly different distance feel.

The bass line (01:06)⁷ settles in $\frac{13}{8}$ with this new stretched groove:

The bass part⁸ already reveals different groupings and accents. Also the ride, snare and bass drum make up for a very natural groove in $\frac{13}{8}$. I had to make choices though on how to divide the $\frac{13}{8}$ for the transcriptions.

These other divisions are useful to perform the tune or to adapt these techniques, this is up to a point because the trio has a unique mastery of balancing complexity and groove awareness without even mentioning the technical level of each musician.⁹

Reducing complexity◊

When you ask musicians to determine the meter and the perceived subdivisions for the second $13$ beats speed of Mystic Brew and Human Nature you will get different opinions with many musicians ranging going for $(5+5+3)$ and a lot of it-doesn’t- matter-you-have-to-feel-it.¹⁰

Considering it as a $(3+2+3+2+3)$ makes it easier to hear because it reflects the groove (bass drum, snare and ride accents and bass line). The piano plays 8th note lines with accents at 01:07 and also uses these accents at 01:22:

For Human Nature which starts as a $\frac{13}{8}$ the original lick is adapted with clear subdivisions at 0:20:

This 3 to 2 ratio can again be found in the Fibonacci sequence. The next one being 5 and 3. Isn’t this exactly what happens when Mystic Brew shifts gears into 21 beats? We now have ($5+3+5+3+5$). At 2:08 when the $21$ speed is already well established the piano plays the following line, which I keep in an 8th note notation on purpose despite the high note density, because Iyer uses the term beats:

The $21$ beat cycle¹¹ is extremely fast and the ride or hi-hat plays a clave pattern. Also note where the snare falls. In $\frac{13}{8}$ it’s on the 4th and on the 9th beat whereas in $\frac{21}{8}$ it is on the 6th and 19th beat. The bass drum also shifts in a similar way preserving the proportions. Thus we get similar spacings in an identical table with the $(3+2+3+2+3)$ or $(5+3+5+3+5)$ groupings:

In Mystic Brew listen for this groove around 03:55 when the $21$ played a second time. Human Nature uses the same device.

How to shift with metric modulations◊

The piano always cues¹² the different speed transitions. The transition from $\frac{8}{8}$ to $\frac{13}{8}$ is quite obvious in the last bar at 01:01. A metric modulation is used by the piano playing a triplet figure on the 4 of bar 3 of the form. One triplet is the new pulse tempo of the $\frac{13}{8}$ meter.

The transition from $13$ to $21$ happens 2 times on Mystic Brew and the piano prepares this a little bit ahead of the drums and bass. The cut seems less clear though. In the Jazz Baltica 2011 Human Nature performance there seems to be a balancing between the $13$ and $21$ before staying in that division. Still at 45:28 it’s possible that Iyer by looking at the rhythm section cues the transition that happens at 45:28.

In the album recording the second time the shift takes place on Mystic Brew there is a call by the piano playing a quintuplet on the last 3 note grouping (03:44):

Now of course these subdivisions are deeply felt and anticipated. The return from $\frac{21}{8}$ to $\frac{8}{8}$ happens quite precisely in one spot at 02:44 preceded by a compressed run on the piano. On a side note, using your DAW to cut sequences out of the two tunes makes for great loops e.g. the transition from $13$ to $21$ (04:17 to 04:25). The band doesn’t actually perform the $21$ back to $13$ transitions but the loop is very smooth.

The musicians will of course layer their own interpretations of the groove, stay in certain divisions, superimpose certain polyrhythms on top of the ongoing complexity or stretch out the transitions. Different live versions illustrate this.¹³. Human Nature from this NPR concert is of particular interest because all the tunes are shortened, a fact Iyer mentions when adressing the audience (32:50).

Why and how◊

The why is easy to answer. Because it is indeed fun, refreshing, challenging and inspiring for the musicians and the audience. The $\frac{13}{8}$ feel taken separately is already something worth exploring. Here my transcription of the first theme of Human Nature (00:49):

At the end of his Guardian article Iyer relates these techniques to specific cultural origins, the classical music of South India (Karnatik music) and expresses his interest in the African roots of African-American music. This is a recurring theme e.g. at the end of the conference with Zakir Hussain¹⁴ or in an interview with Asaf Sirkis.¹⁵

In the later (53:20) Iyer talks about the stamp of his compositions “rhythmic intrigue”. It’s worth concluding with a quote:

“I don’t think of it as complexity so much as something to work with … I wanted to bring together those sensibilities, the polyphony of West African and African American music with these kind of additive techniques that you find in Karnatic and Hindustani music … and we can [use] these layers with creole systems that have a cyclicality but also this richness.”

In order to link these techniques more specifically to the Karnatic approach we could say that the shifts are changes of Gati defined as “the subdivision of the beat into an equal number of units called matras"¹⁶ i.e. tuplets. Another approach, and this is also guesswork on my part, would be to consider that in the 2 tunes presented here a single beat is divided either into $8$, $13$ or even $21$ beats. This would approach it to the use of other types of Gatis $9$, $11$ and $13$ that percussionists from South India¹⁷ have been using since the 80^ties. But this explanation lacks because it breaks the tala concept. So a better interpretation might be found in actual South Indian Music practices where the tala itself changes during a piece. (cf. introduction update from November 7th 2022 on the change of Gati interpretation).

Yet another way to of considering the shifts, and these applies in particular to the $21$ division is to dive into the concept of morphing and it’s implication on mutating tuplets. Part 2 will take a look at another life version and at the applications of these techniques.¹⁷