What are the key features of Minimalist music?

Minimalist music is a style of composition developed in the 1960s in the USA, as a rejection of the atonal style of other experimental composers of the time. The most important composers of this style were Terry Riley, Steve Reich and Philip Glass. Their music is characterised by repetitive processes, creating large-scale works from very small cells of musical material. Harmonically this music is often very tonal and static, sometimes using drones (low, sustained harmonic tones). Later composers such as John Adams and Louis Andriessen were heavily influenced by this style, and integrated these techniques with other styles like Jazz and Romanticism. Terry Riley's "In C" is one of the seminal minimalist works, and it contains many common mimalist techniques such as a constant pulse, played by octave Cs in the piano, small cells of music which are repeated many times, and a C tonal centre throughout the work. Steve Reich was influenced greatly by African rhythms when he visited Ghana, and this influence is evident in his works for percussion such as Drumming. Both Steve Reich and Philip Glass started out with their own ensembles, "Steve Reich and Musicians" and "The Philip Glass Ensemble". Philip Glass is well-known for his operas, such as Einstein on the Beach, and his symphonic works (12 symphonies in total). When listening to or analysing minimalist music, make sure you look out for repeated ostinato cells of music, slow harmonic rhythm (static harmony), little variation in pitch or register and complex rhythmic processes which develop over the course of a piece.