Garth works as a composer, arranger, musical director and studio programmer. Theatre companies he has worked for in N Ireland include 4 Front, InterActors, Blue Box (BIFHE), The Rainbow Factory (school of performing arts / company), Red Lead Arts, Cahoots NI and Youth Lyric.

In 2005 he was resident musical director with Red Lead Arts, based in his homeland of N Ireland, where he composed jazz / modern music for The Blackout Show, co-written by Marie Jones. Garth has had many credits as composer/MD over the past few years including Darkie, by Damien Gorman, (Blue Box Theatre Company) which featured live contemporary music and toured theatres in the summer/autumn of 2005, culminating in performances as part of the Belfast Festival at Queens., and the Travelling Teller (Cahoots NI), with programmed / electronic music, touring major theatres in Ireland.

Garth has also taught music theatre at higher national diploma level and music at secondary level and has worked as an arranger / programmer alongside prominent Irish producer / pianist, Brian Connor (Riverdance / Van Morrison), on albums by such varied european artists as Colin Reid (Ireland) and Tom Roger (Norway). He has just finished working as a composer/arranger on Twelfth Night (Youth Lyric) and is currently composing contemporary classical and ambient/electronic music for a new production of Joshua Sobel's Ghetto, for the Rainbow Factory and also remixing for a Canadian rock band called The Other Children.