It exists perhaps most prominently in its versions for violin, string orchestra, and percussion and for violin and piano. Most other versions are very similar to these two: for instance, the versions for viola and piano and cello and piano are almost exactly the same as the former, whereas the version for string quartet is more similar to the latter.
The first version string quintet and wind quintet was written in 1977. Further versions were written over the years up to about 1992.
Structurally, Fratres consists of a set of nine chord sequences, separated by a recurring percussion motif. The chord sequences themselves follow a clear pattern, and while the progressing chords explore a rich harmonic space, they nevertheless appear to have been generated by means of a simple mathematical formula.