Details are scant tho' of course we know Elton John played organ on 'Perfect Lady Housewife' - and very possibly it was Peter Robinson playing organ on 'Frightened Lady' and 'I Wanna Shout'- assuming it's the same Peter Robinson of the band Quatermass who later played organ on the Distant Light track 'Hold On' then the Romany Tracks; 'Slow Down' and 'Won't We Feel Good'
Jim Jewell was an old friend of Bobby's and was in Gallagher & Lyle's band later, we know he plays sax on 'Look What We've Got' and later on a few Polydor albums
- Tony Coe (later featured on 'Hello To Romance') was in C.C.S. along with Blue Mink's guitarist Alan Parker (who played on 'I Shall Be Released'), and bassist Herbie Flowers (who contributed to 'Distant Light' so I have heard plus Allan's solo albums) - fellow C.C.S. member Ronnie Ross played brass on 'Blowin' in The Wind' (with Ronnie Scott) so a clear Hollies / C.C.S. link exists and Tony Coe might well have helped out uncredited
Henry Lowther (of Manfred Mann, MM Chapter Three) later plays brass on the 'Russian Roulette' album for them so he too might figure (earlier Henry being a colleague of 'one off' Hollies bassist Jack Bruce in The Manfreds in 1966) so an old link back to the sixties with The Hollies probably existed and Henry (who played Trumpet if I recall correctly) might have been another uncredited friend - mostly it's just a blanket credit going to Johnny Scott, Mike Vickers (another former Manfred who played saxophone besides guitar and flute), Lou Warburton or Alan Tew for providing 'additional accompaniment' etc...
Clearly The Hollies had many 'name' musical friends going right back to the early sixties so those I've mentioned were possibles each being 'veterans' of the sixties music scene - but as I said besides those credited later or what was later advised in many instances the actual details remain scant especially over that 1970-71 period
- Blue Mink's keyboardist Roger Coulam played piano on 'Hey Willy' of course so he might well have contributed further than is credited...
They did work with some famous figures on recording sessions that we know little of - for example I have a handwritten note from Tony Hicks in 1981 stating;
'we have recently been recording with Graham Nash ('Somethin Ain't Right'), John Miles ('Carrie') and Phil Lynott (??) ...'
What the Phil Lynott connection was remains unknown maybe Phil was just playing some bass guitar for them - but there is no 'official' credit for Phil Lynott playing with The Hollies tho' per Tony back in 1981 he was...
there are photos of Tony with Phil Collins, Bobby and Paul Weller etc...