[9] In Autumn 1975, Haynes founded the ten-piece British jazz rock band RedBrass,[4][10][11] initially as an offshoot from the left-wing theatre ensemble Belt & Braces Roadshow.
[12][13] RedBrass was celebrated for the social and political content of Haynes's compositions[14] and became one of the most ubiquitous groups on the jazz scene, earning praise from Melody Maker and The Times.
[19] Haynes's imaginative vocal arrangements for three female singers were key to the group's distinctive sound, which incorporated Latin percussion, jazz-flavoured brass, a rock-rhythm section, unaccompanied harmony singing, and relatively unusual instruments including the glockenspiel, tubular bells, timbales and spoons.
[14][20] Grand Union was founded to reflect the UK's changing cultural landscape, and to create a space for young musicians from diverse backgrounds to collaborate with top level jazz players.
[20] As the company's artistic director, Haynes was known for harmoniously blending different genres and styles,[4] and adapting the big band format for community education ventures, cultural exchanges, extended commissions, and collaborations.
[25] Haynes's compositions have been broadcast in full multiple times on BBC Radio 3, including The Rhythm Of Tides (1997), Now Comes The Dragon's Hour (1999), Where The Rivers Meet (2000), If Paradise (2003), and The Golden Road, The Unforgiving Sea (2011).
[28] Haynes was a tireless supporter of community music, and used both Grand Union and RedBrass as the professional core of many bold initiatives involving youth bands, amateurs and folkloric groups of all kinds, for which he gained a reputation as an inspired enabler.
[29] He wrote a regular blog describing his approach to music-making and analysing his compositional techniques; he taught music degree students at Trinity College London and made several programmes on jazz for the BBC.
[4] Haynes was of the opinion that, in the fast-changing demographic of Britain today, migrant and migrant-descended musicians can and should have a profound artistic and educational influence on British culture,[7] and called for greater recognition for the work created for local, diversely rich communities.