Fratres (Brothers) is a composition by the Estonian composer Arvo Pärt exemplifying his tintinnabuli style of composition. It is three-part music, written in 1977, without fixed instrumentation and has been described as a "mesmerising set of variations on a six-bar theme combining frantic activity and sublime stillness that encapsulates Pärt's observation that 'the instant and eternity are struggling within us'."
Structurally, Fratres consists of a set of eight or nine chord sequences separated by a recurring percussion motif. The sequences themselves follow a pattern, and while the progressing chords explore a rich harmonic space, they appear to have been generated by means of a simple formula. Authorized versions of Fratres are as follows: