In 1994 Marsh and his wife, the singer Anna Myatt, co-founded and directed the music theatre ensemble Black Hair.
[5] His students include John Abram,[6] Tom Armstrong,[7] Richard Causton,[8] David Power,[9] Andrew Hugill,[10] Shu-Yu Lin,[11] Aaron Moorehouse,[12] Akiko Ogawa,[13] Felipe Otondo,[14] Andy Quin[15] and Paul Whitty.
[3] Between 2002 and 2006 Marsh composed vocal settings of all fifty of the Pierrot lunaire: rondels bergamasques cycle of poems by Albert Giraud.
Marsh's contributions included the solo piece Dum, performed inside a cage or at a lectern with many metal objects by (among others) Alan Belk of Vocem and the composer himself.
[3] Humour and irony are important elements, as shown in a series of works derived from Old Testament stories and themes presented in contemporary terms, such as the dramatic oratorio Samson (1984 - closer in style to Japanese Noh drama than the European oratorio), the melodrama The Song of Abigail (1985) and the extended drama The Big Bang (1989) - subtitled "Tales of love and intrigue; a kaleidoscope of sex and violence".