INSIDE THE MUSIC
Key: E (mixed mode) Novel features: non-isochronic 5/8 and 6/8 meter, ‘Mixodorian’ mode Tempo: dotted crotchet ≈73bpm, crotchet ≈110bpm
As we’ve seen – despite listener (and transcriber) mis-hearing – the vast majority of this album (and Led Zeppelin’s output) is in straight-up 4/4 time. It is, however, made more dissonant with significant use of syncopation, grouping dissonance and irregular section length. Black Dog includes irregular length bars, and these result in a shifting and ‘resetting’ of bar lines. However, the beat itself – the underlying heartbeat of the music – is always regular. It has an isochronic (‘equal time’) beat.
Four Sticks, conversely, is a clear example of non-isochronic beats – where the listener and performers experience a pattern of changing beat lengths in order to absorb the rhythm. Here, all the meters can be perceived in terms of strings of two, three or six semi-quaver rhythmic units, (which we will call ‘long’ and ‘short’ pulses respectively). The construction of meters through the addition of small rhythmic units is known as ‘additive meter’ and is a staple of North African, Eastern European, Mediterranean and other traditional music forms. It has found its way into the Western pop, rock and ‘classical’ forms through, for example, Dave Brubeck’s Turkish influenced Unsquare Dance and Take Five, compositions of Bartok, Stravinsky and Zappa, The Beatles’ Here Comes The Sun, the Mission Impossible theme, and the music of Radiohead and, frankly, anything under the prog/post-prog umbrella.
In Four Sticks there are two metric groups (A and B) presented; an ‘asymmetric’ 5/8 bar made up of two long and two short beats (3 + 3 + 2 + 2 = 10 semi-quavers), and a symmetrical 6/8 bar which can be thought of as two groups of three short beats ([2 + 2 + 2] + [2 + 2 + 2]), or even just two groups of six. Illustrated below. These dissonant asymmetric – and more constant symmetrical – patterns are interchanged and collectively make up the entirety of the shifting but perfectly accessible metric background.
Another interesting aspect of this track is in its use of modality. The root of the key is E, and the central mode is largely E Dorian (E, F#, G, A, B, C#, D). However, the G is very often teased up to a G#, creating a more joyful E Mixolydian. This mixed-mode blending of Dorian and Mixolydian is a common feature of blues-rock harmonic language (and sometimes called ‘Mixodorian’), and here even expands to include a D#. The idea of a ‘cluster’ of modes that share the same root note is known as ‘modal interchange’ or ‘parallel modes’, a device also used in the next track.