Listened to Steve Reich’s Music for Pieces of wood (which requires tuned claves). His style is to set up a rhythmic pattern and then subtly undermine it with a cross-rhythm. If the asynchronised rhythms start to converge again this is like ‘entrainment’ in classical mechanics theory of oscillators – why two mechanical clocks on the same wall with the same pendulum length will converge to beat in time:
This inspired me to think about planning a percussion piece with the bar (for notational simplicity, a pair of bars) representing the average interval between high tides; the time of high and the low tide represented by wood blocks at two distinct pitches (temple blocks?) diverging outside and inside the bar. Depending on temp this needs to be rounded to the nearest demi- or semiquaver. The tidal range varies with the lunar cycle and this can set dynamics in the obvious way. The highest and lowest tides (spring tides) have the largest intervals about them. Assuming also a side drum (or pair of side drums handing over between each other, for practicality), playing at 12 quavers in half a day, and also that the average time between tides is 12.5 hours, then the basic bar pattern is 12/8 alternating with 13/8, and a Reich-like progressive syncopation is set up as a day ‘beat’ say on triangle every 24 quavers, returning to synchrony after (2 x (12+13) = 50 bars
Added interest can be from bass drum for waves overspilling the promenade (randomly chosen around ‘spring high tides) and by contrast a suspended cymbal roll around neap tides – e.g. sand blowing in the wind. A speaker could say the tide height in metres at spring high and low tides – the whole piece ending after some multiple of the lunar month 28 days to say ‘come in number 56’ or 84 – to fit allowed length. 84 lunar days (around three months) would last 168 bars at dotted crotchet = 100 is nearly 7 minutes; a reasonable performance length for the audience to get the hang of the shifting rhythms and not get bored. For comparison, Steve Reich’s piece is 9 minutes on youtube.
A tide table for three months at Aberystwyth is:
The source for this was entitled ‘Discover Ceredigion’ which could be the working title of the piece: