An ostinato is any melodic, rhythmic or chordal phrase, usually short, that’s repeated continuously through a section of a work, or through the whole piece.
Minimalism could be described as ‘the triumph of the ostinato’. (It’s been called a lot worse things than that.) But minimalism is a bit of an exception in Western classical music in that in its purest form it’s nothing but ostinato.
With all due respect to Philip Glass’s Facades, Terry Riley’s In C and Steve Reich’s Drumming, the interest normally begins when the unchanging, ‘obstinate’ element rubs up against ideas that do change and develop – a key ingredient in Western music since the renaissance.
Passacaglias (or chaconnes) are based on ostinatos – the repetitive, circular pattern created by the ostinato figure underlies a melodic line that rises and falls, develops and recapitulates according to different laws.
The ostinato defies the passing of time, the developing element celebrates it. Result? Tension. GK Chesterton called it the beauty of the bent bow: bowstring and wood pulling in opposite directions, creating the exquisite arc.
Take ‘When I am laid in earth’ from Purcell’s Dido and Aeneas. Dido’s line aspires and plunges, aspires and sighs with the fluid drama of her emotions. Underneath, the unchanging passacaglia bass circles inexorably, like fate.
In Chopin’s E minor Prelude (No. 2), the harmonies of the left hand’s ostinato do change gradually, but the rhythmic pattern remains constant, defying the rhythmic freedom of the right hand’s quasi-vocal phrases.
In the Chopin, the pattern eventually fragments, pathetically. At the other extreme, the five-in-a-bar rhythmic ostinato that drives ‘Mars’ from Holst’s Planets finally triumphs, like the God of War crushing all before him.
Obstinate repetitions, harmonic, melodic and rhythmic, run throughout Stravinsky’s Rite of Spring and Les Noces, generating huge physical excitement. But the hushed final hymn of his Symphony of Psalms shows another possibility.
The hymn melody itself is based on repetition, but in the bass another figure rotates in a different metre (four beats against the hymn’s three). Here is tension, but between two ostinatos.
The result is something calmly beautiful, mesmeric, changing yet timeless.
This article was first published in the October 2012 issue of BBC Music Magazine. The illustration is by Adam Howling