They also shared billing with acts such as Rory Gallagher, Rush, Kiss, The Eagles, Free, Bo Diddley, Strawbs, REO Speedwagon, Electric Light Orchestra, Lynyrd Skynyrd, Frank Zappa and the Mothers of Invention, Uriah Heep, Grand Funk Railroad, Rod Stewart, The Faces, Black Sabbath, Taste, Brinsley Schwarz, Atomic Rooster, Traffic, Mott the Hoople and many more.

[4] The albums If 3 (1971) and If 4 (titled Waterfall in US with one different track) (1972) were accompanied by heavy touring schedules in the States and Europe, especially in Britain and Germany, where the band appeared on TV (BBC's Top of the Pops/Old Grey Whistle Test in the UK) and one of their tracks was used as a signature tune for the news in Germany, as well as performing live (September 1971) on Bremen TV's Beat-Club.

Consisting of essentially two clearly defined line-ups, as well as an intermediate, transitional one, the original band had a heavier leaning towards jazz, and was formed by Dick Morrissey, on tenor sax and flute, and Terry Smith on guitars, both Melody Maker award-winning British jazz musicians who had played together in US soul singer J.J. Jackson's band with Dave Quincy on alto and tenor saxes, together with Spike Wells on drums, Lionel Grigson on keyboards and Daryl Runswick on bass, although these last three musicians did not record with the band, with Wells going off to join Tubby Hayes.

The definitive seven-piece line-up for the first incarnation of the band, with a more jazz-rock-oriented style, and which appears on the first four studio albums, as well as a live recording, was J. W. Hodkinson on lead vocals, John Mealing on keyboards, Jim Richardson on electric bass, Dennis Elliott on drums, with Dave Quincy on alto and tenor saxes, Terry Smith on guitars, and Dick Morrissey on tenor and soprano saxes and flute.

If finally broke up in 1975, Dick Morrissey going on to work with the Average White Band and Herbie Mann, eventually forming Morrissey–Mullen; Geoff Whitehorn to join Crawler and, subsequently, Procol Harum.

Other members worked with Ted Nugent, who was also produced by Lew Futterman: Gabriel Magno (1973–1974), Cliff Davies (1975–1980) and Walt Monaghan (1979).