[citation needed] For decades Hennessy has seen advocacy of the music of Douglas Weiland as his primary artistic responsibility.
He also continues to advocate for the music of the Australian composers Richard Mills AM, Calvin Bowman and Benjamin Martin.
[citation needed] Other positions previously held include Head of Strings at the University of Melbourne, concertmaster of the Tasmanian Symphony Orchestra, deputy leader and founder member of the Australian Chamber Orchestra, member of the London-based Academy of St Martin in the Fields, faculty member of the Australian National Academy of Music, and founder/director of the Tasmanian Symphony Chamber Players, the Melbourne University Chamber Orchestra, and the Adelaide Youth Chamber Orchestra.
[citation needed] He has made hundreds of concerto appearances and has been recognised as one of Australia's leading violinists and music educators.
[citation needed] In the 2018 Queen's Birthday Honours William Eldred Hennessy was appointed a Member of the Order of Australia for "For significant service to music as a concert violinist, artistic director, mentor and educator".