[3] Starting in 1963 as bassist with The Daevid Allen Trio, alongside drummer Robert Wyatt, he alternated between free jazz and rhythm and blues.

In 1964 with Brian Hopper (his brother), Robert Wyatt, Kevin Ayers and Richard Sinclair he formed The Wilde Flowers, a pop music group.

"[6] After leaving Soft Machine, through the end of the 1970s, he worked with such groups as Stomu Yamashta's East Wind, Isotope, Gilgamesh, and the Carla Bley Band.

[2] In the early 1980s Hopper gave up playing music for a couple of years, but by the mid-1980s he was actively working with several bands, including Pip Pyle's Equipe Out and Phil Miller's In Cahoots.

Also in 2002–04, Hopper, Dean and two other former Soft Machine members (drummer John Marshall, and guitarist Allan Holdsworth) toured and recorded under the name SoftWorks.

Other occasional projects were Soft Bounds (with French musicians Sophia Domancich and Simon Goubert, first with Elton Dean and then Simon Picard), which like PolySoft released a live CD recorded at the Triton club, and Clear Frame, an improvising group with Charles Hayward, Lol Coxhill and Orphy Robinson (augmented for their first release by Robert Wyatt on cornet).

Hopper recorded two solo albums for, and established an online shop via, the highly regarded UK-based internet label, Burning Shed.

[7] A Hugh Hopper benefit concert took place in December 2008 at the 100 Club in London and featured In Cahoots, members of Soft Machine Legacy, Delta Sax Quartet, Sophia Domancich and Simon Goubert, Yumi Hara Cawkwell, and the Alex Maguire Sextet.