The Harmony of Clashing Tempos

Question

The jazz guitarist John McLaughlin once published a book of scores for a number songs that he composed for his Mahavishnu Orchestra. There are some very unusual theoretical conundrums that come up when reading these songs, and I'd like to ask about one such issue that appears in his score for the song "On The Way Home To Earth."

For the first part of the song, we are told that guitar, drums, and bass vamp for 2 1/2 minutes with a quaver BPM = 304.

Then comes the second part. While the first part continues, an orchestra appears by voicing a number of whole note chords in the quaver BPM = 138.

Strange mix, no? Well, on the bottom of the score we find a curious note:

NOTE: The tempos are not related, for when correctly played, one will notice the creation of tension and its release as the slow tempo gradually envelops the fast.

Can someone explain this harmony/entropy of tempo? Is McLaughlin suggesting that the musicians from the first part will naturally adjust their playing to meet with the orchestra's playing? Or is their some kind of musical force that explains how slow tempos envelope fast tempos when listening to their sonic clash?

Answer 1

is their some kind of musical force that explains how slow tempos envelope fast tempos when listening to their sonic clash?

No, there is no musical theory which states this.

Is McLaughlin suggesting that the musicians from the first part will naturally adjust their playing to meet with the orchestra's playing?

No, what he means is that, by crescendoing dynamically from the background to the foreground, the slower tempo will take over the listener's attention. It's due to the dynamic and textural changes that the slower tempo becomes dominant.

Can someone explain this harmony/entropy of tempo?

I will be extremely brief, but tempos can be thought of as dissonant vs. consonant to one-another based upon the common denominator. For example 120 and 240 are "consonant" because one is twice the speed of the other. 60 and 90 are a bit more dissonant, but still related by a 3/2-multiple (i.e. you will still have regular coinciding beats and barlines).

In your example 138 and 304 are entirely dissonant because there is no multiplier that can relate them to one another. One would have to wait a very long time for barlines in the two tempos to coincide.

These tempos would seem to have been chosen specifically by the composer for this dissonant effect of non-correlated tempos

Answer 2

Without looking at the score, here's my guess:

Let's say you have an experimental song where there are two main lines playing in 2/4. They both start at the same time, but one of them has a one beat pick-up while the other doesn't. Both lines change chords every two beats.

The chord progression might be written like this:

Line 1: C Maj | F Maj   F Maj | A Min   A Min | C Maj
Line 2: C Maj   C Maj | E Min   E Min | C Maj   C Maj

So now we have a situation where a chord in one line is dissonant with the other line for one beat, but consonant the next beat. For example, the E minor chord in the second line will be very dissonant with the F major chord it comes in on, but consonant with the A minor chord the first line transitions to.

My guess is that the two sections of the song in different tempos have a similar relationship in "On The Way Home To Earth." McLaughlin may have deliberately written the chords the orchestra plays so that they are consonant with the faster rock group at times and dissonant at others. The fact that they play at different tempos allows this tension to be especially complex.

EDIT: I just listened to the piece. It sounds like in addition to what I wrote above, you can interpret the rock section and the orchestral section independently. The rock section has its tension and releases, as does the orchestral section. Since the orchestral section is so much slower, though, it has more sway on whether the song is consonant or dissonant. Even as the rock section quickly builds and releases tension, if the orchestral section is playing a dissonant chord, the entire piece sounds tense at that moment and won't release that tension until the orchestral section resolves.