Born in Bog Meadow, West Belfast, he started his musical career there in the early 1960s as guitarist with the Manhattan Showband, alongside his friend Van Morrison.
The band gained a residency in Blackpool, and wrote and recorded the original version of "Bad Little Woman", later covered in America by The Shadows of Knight.
[3] Armstrong and his bandmate and songwriting partner, singer and bassist Rod Demick, then joined Screaming Lord Sutch's band, known at the time as the Beautiful Quality, for six months in 1967.
Demick and Armstrong continued as a duo under their own names, and released several singles and two albums, Little Willy Ramble (MAM, 1971) and Lookin' Through (A&M, 1972), described by Allmusic reviewer Craig Harris as "impressive".
[2] After Noosha left Fox, Armstrong and Young formed a new band, Yellow Dog, with guitarists Andy Roberts and Jim Gannon, bassist Gary Taylor, and drummer Gerry Conway.