There has been some question as to the AMM lineup at various points in their history.  It is a complicated issue considering that the group has been around for nearly fifty years now and has constantly changed its membership over the years.  Additionally there have been plenty of guests, members at large and collaborative performances to further complicate the issue. Over the course of my reviews of the various bootlegs floating around I have made various assumptions w/r/t to the line up on a particular recording, some of which have conflicted with the information circulating with the sources.  In general the information that comes with the sources is highly suspect – they simply use information that is highly generalized or from sources that are not particularly accurate (the AMM page on Wikipedia is fairly useless for instance).  My process is to always start with principle sources, amend it with secondary sources and then to finally rely on the evidence of my ears. Based on this process I have complied the following timeline of AMM’s membership, all of which is verified via the sources cited.

AMM Timeline

Proto-AMM

Early 1965
Keith Rowe, Edwin Prévost, Lou Gare(1)

AMM

Mid 1965
Keith Rowe, Edwin Prévost, Lou Gare, Lawrence Sheaff (1, 5)

1966 to mid-1967
Keith Rowe, Edwin Prévost, Lou Gare, Lawrence Sheaff, Cornelius Cardew (1, 2)

Cardew officially joins in January(2; p. 254)

Mid-1967 to April 1968
Keith Rowe, Edwin Prévost, Lou Gare, Cornelius Cardew (1, 2, 8)

Lawrence Sheaff leaves group a few months after recording AMMMusic (8, 5, 1; p185) probably April 20th 1967

April 1968 to 1969
Keith Rowe, Edwin Prévost, Lou Gare, Cornelius Cardew, Christian Wolff, Christopher Hobbs (1, 2, 5)

Christopher Hobbs joins April 1968 (2; p. 304)
Christian Wollf’s Sabbatical Year(1; p.185, 2; p.304)
John Tilbury filling in for Cardew at times
(1; p.185)

1969 to May 1971
Keith Rowe, Edwin Prévost, Lou Gare, Cornelius Cardew, Christopher Hobbs (1, 2, 5)

Hobbs leaves the group in May 1971(2, p.650)

May 1971 to March 1972
Keith Rowe, Edwin Prévost, Lou Gare, Cornelius Cardew (1, 2; p.650)

March 26th 1972 – final AMM show(2; p. 651)

AMM: double duos

March 1972 to January 1973

The occasional double AMM:  Edwin Prévost, Lou Gare and Cornelius Cardew, Keith Rowe(1, 2; p. 651)

AMM II

mid-1972 to 1975
Edwin Prévost, Lou Gare (1, 2, 3)

AMM

Summer 1976
Keith Rowe, Edwin Prévost, Lou Gare, Cornelius Cardew(1; p.186, 2l p.816)

Unrecorded, no performances, practices only, which apparently didn’t work out.

AMM III

1977 to 1979
Keith Rowe, Edwin Prévost (1, 2, 3)

(1979/80:  Supersession: Evan Parker/Keith Rowe/Barry Guy/Edwin Prévost)

AMM

late 1980 to 1986
Keith Rowe, Edwin Prévost, John Tilbury  (1, 3)

1986 to 1994
Keith Rowe, Edwin Prévost, John Tilbury, Rohan de Saram (1, 3)

1989(?) to 1992
Keith Rowe, Edwin Prévost, John Tilbury, Rohan de Saram, Lou Gare(4)

1994 to mid-2004
Keith Rowe, Edwin Prévost, John Tilbury

May 1st 2004:  Final AMM show

AMM IV

2005 to present
Edwin Prévost, John Tilbury

Explanations

Beginnings
The sixties are of course the most contentious, being a long time ago and featuring the largest amount of changes. Cardew joining, Sheaff leaving in 1967, Hobbs and Wolff joining and then the fracture in the 70s. Tilbury’s Cardew bio goes a long way to providing specific dates for some events though others remain somewhat vague (no specific date for Sheaff leaving the group for instance just “April 1967, though his last concert with the group is mentioned, as being at the Commonwealth Institute which the Factsheet(5) lists only one in April on the 20th.

1968 to 1970
The information that I begin with for AMM from 1968 to their breakup in 1972 is primarily sourced from Prévost’s article AMM 1965/1994 — a brief and mostly chronological historical summary published in No Sound is Innocent(4) :

In 1968 American composer Christian Wolff joined the ensemble for the duration of his sabbatical year in Britain. Also during this time Christopher Hobbs, a percussionist and composition student of Cardew’s, at the Royal Academy of Music, regularly performed with AMM. John Tilbury occasionally participated when Cardew was not present.

From the early 1970s until the fracture of AMM in 1972 the ensemble remained the quartet: Cardew, Gare, Prévost and Rowe.” (4, p.185)

1969 is a question: was Christian Wolff’s “sabbatical year” – was it a school year, so Autumn 1968 to Summer 1969? Or was it literally 1968?  Additionally by saying that Hobbs played “during this time” does Prévost mean exclusively during Wolff’s time? Considering that Hobbs is part of the group for The Crypt sessions (12th June, 1968) but not Wolff I’d say this is the case.  This is further backed up by the fact that Hobbs was part of the group ion December 1969 when they played in Denmark as released as part of the Laminal box set. Thus I think that that sentence is too compress, it seems that Hobbs was a part of AMM from 1968/1969 presumably starting around the time that Wolff did. Alas there are no AMM recordings floating around with Christian Wolff , leaving this as one of the most egregious missing eras in the historical record. In the various bootlegs floating around It seems to be generally assumed that Hobbs is still part of group in 1970 and there has been some question as to why I don’t always follow this assumption. Again it is the above quote that by “early 1970 the ensemble remained the quartet”.  Clearly Hobbs left at this point but what exactly qualifies as the “early 70s”? Of the two bootlegs that I have in question from this period (Jan. and Feb. 1970) it sounds like there are two percussionists in the January recording and only one on the February recording. Thus I make the cutoff here.

1970s
In the 70s the originally group came to an end but several interesting events occurred. First off due to prior commitments the group had a tour and a festival in the Netherlands. With irreconcilable differences between the Rowe/Cardew and Gare/Prévost camps they played as the double duos. Gare/Prévost presumably playing as they would in AMM II but the Cardew/Rowe duo is completely unheard at this point. The record indicates that they were more in the traditionally abstract AMM realm (as opposed to Gare/Prévost’s more ‘free jazz’ sound) and would often play over tapes of the Peking Opera and other such revolutionary sound musics). AMM II would be the other major event of the mid 70s, this was the continuing duo of Gare and Prévost, who constantly got billed as AMM so they rolled with it. At the end of the 70s when the duo of Rowe and Prévost formed they used AMM III a the moniker indicated that the Gare/Prévost duo was AMM II, which I’ve used throughout.

The most strange and interesting things though occurred in 1976 when Rowe made an attempt to get the quartet back together again. There was a concert on April 1st of that year that Rowe refers to as a “hidden” AMM concert that included himself, Cardew and Prévost plus flautist John Wesley-Barker and double-bassist Marcio Mattos(2; p. 816). This event has been heretofore unknown only revealed in Tilbury’s massive Cardew biography.  The other event, more well known, was a series of practices in June of 1976 of the quarter of Gare, Cardew, Prévost and Rowe(2; p.816).  These apparently didn’t work out and Tilbury cites Gare as feeling that Cardew didn’t have the level of commitment necessary and abandoned the attempt.

1980s
This is basically the question of Rohan de Saram. He was definitely considered part of the group, but he clearly was the one with the most demanding schedule (being a member of the Arditti String Quartet at this time) and thus there are cases of the trio AMM as well as a quartet with Lou Gare.  There also are various lineups with the clarinettist Ian Mitchell (quartet and quintet with de Saram) but I tend to think of those as more guest spots as I would the occasional shows with Evan Parker.

1989 to 1992
The early 90s quintet AMM was something I only stumbled upon during the course of this review process. I have a bootleg from 1987 from this quintet and in the course of my research I found this line in the updated CD liner notes accompanying the CD release of The Crypt:

“And the band goes on: for to date we have still not recorded the current quintet line-up of de Saram, Gare, Prévost, Rowe and Tilbury.” – Edwin Prévost, Februrary 1992(5)

This version never would be recorded and it seemed that Gare left again soon after. De Saram would soon follow though there would be the occasional gig through at least 1994.

AMM IV
After Rowe left AMM in 2005, Tilbury and Prévost made the controversial decision to continue on as AMM as a duo. I refer to this as AMM IV as per Rowe’s definition that AMM should be at least trio with himself and Prévost at the core.  It is interesting to note that AMM IV now often plays with other musicians but they are always listed as “AMM+” indicating that these are all guest spots. These guests have included Sachiko M, Christian Wolff and John Butcher among others (see the comments for more info).

References

1) Edwin Prévost, No Sound is Innocent, Copula, 1995
2) John Tilbury, Cornelius Cardew: A Life Unfinished, Copula, 2008
3) Notes on AMM: Entering and Leaving History Stuart Broomer, CODA Magazine no. 290. 2000
4) Edwin Prévost, The Crypt Liner notes, 1992 (Matchless)
5) AMM FactsheetThe Crypt Liner Notes (not online), Matchless Recordings 1992
6) The AMM page at the European Free Improvisation Home
7) Meta Machine Music, Rob Young, The Wire Issue #132 (February 1995)
8) Edwin Prévost, AMMMusic Liner Notes (originally published in RER Quarterly vol.2 no.2, Nov. 1988)