Sixty-four orchestras have been members of ICSOM at some time. There are currently 51 member orchestras.
The following orchestras, active in the formation of ICSOM and represented at meetings which preceded the formal adoption of bylaws establishing membership in 1963, were accorded charter member status in the bylaws. They are arranged in order of first meeting attended; within that classification they are listed alphabetically.
- Boston Symphony Orchestra (May 1962)
- Chicago Symphony Orchestra (May 1962)
- Cincinnati Symphony Orchestra (May 1962)
- Cleveland Orchestra (May 1962)
- Indianapolis Symphony Orchestra (May 1962)
- Los Angeles Philharmonic (May 1962)
- Metropolitan Opera Orchestra (May 1962)
- New York Philharmonic (May 1962)
- Philadelphia Orchestra (May 1962)
- Pittsburgh Symphony Orchestra (May 1962)
- Saint Louis Symphony Orchestra (May 1962)
- Toronto Symphony Orchestra (May 1962-1971) (withdrew)
- Baltimore Symphony Orchestra (September 1962)
- Detroit Symphony Orchestra (September 1962)
- Minneapolis Symphony Orchestra (now Minnesota Orchestra) (September 1962)
- Rochester Philharmonic Orchestra (September 1962)
- Buffalo Philharmonic Orchestra (June 1963)
- National Symphony Orchestra (June 1963)
- San Francisco Symphony Orchestra (June 1963)
The following orchestras became members in the years indicated. Before current policy was instituted, an orchestra could be granted membership in mid-season and was not required to send a representative to the annual conference at the time it joined. Hence some orchestras listed were not represented even long after becoming members, while some orchestras sent observers to conferences before becoming members.
- Houston Symphony Orchestra (1965)
- Kansas City Philharmonic (1966-1983) (folded; superseded by Kansas City Symphony; see below)
- Seattle Symphony (1) (1966-1989) (formally notified of loss of eligibility on 27 March 1989)
- Honolulu Symphony Orchestra (2) (1967)
- Dallas Symphony Orchestra (1968)
- Denver Symphony Orchestra (1968) (became Colorado Symphony Orchestra in 1989)
- Montreal Symphony Orchestra (1968-1975) (joined OCSM)
- New Orleans Philharmonic (later New Orleans Symphony) (1968-1992)
- (folded; superseded by Louisiana Philharmonic)
- New York City Ballet Orchestra (1968)
- San Antonio Symphony (3) (1968-1970, rejoined 1978)
- Vancouver Symphony (1968-1975) (joined OCSM)
- Lyric Opera of Chicago (1969)
- Milwaukee Symphony Orchestra (1970) (joined during preceding season)
- New York City Opera Orchestra (1970) (joined during preceding season)
- Syracuse Symphony Orchestra (1970)
- New Haven Symphony (1970-1977) (not listed after 1977)
- Atlanta Symphony Orchestra (1971)
- Oregon Symphony Orchestra (1971)
- Winnipeg Symphony (1971-1975) (joined OCSM)
- North Carolina Symphony (1972)
- New Jersey Symphony Orchestra (1973)
- Florida Symphony Orchestra (1974-1992) (folded)
- Phoenix Symphony Orchestra (1974)
- San Diego Symphony Orchestra (1974)
- Birmingham Symphony (later Alabama) (1975-1995) (folded; reconstituted in 1997; rejoined in 1998)
- Nashville Symphony Orchestra (1975-1977) (not listed after 1977; rejoined in 2000)
- Oakland Symphony Orchestra (1975-1990) (reconstituted, joined ROPA as Oakland East Bay)
- Grant Park Symphony Orchestra (1977)
- Hartford Symphony (1977-1980) (voted in December 1980 to discontinue membership)
- Oklahoma Symphony Orchestra (1977-1989) (folded)
- San Francisco Ballet Orchestra (1977)
- Toledo Symphony Orchestra (1977-1987) (joined ROPA)
- Kennedy Center Opera House Orchestra (1978)
- Utah Symphony Orchestra (1979) (became Utah Symphony and Opera in 2002)
- Louisville Orchestra (1980)
- San Francisco Opera Orchestra (1983)
- Saint Paul Chamber Orchestra (1984)
- Florida Orchestra (1987)
- Columbus (Ohio) Symphony Orchestra (1990)
- Philharmonic Orchestra of Florida (now Florida Philharmonic Orchestra) (1990) (folded 2004)
- Jacksonville Symphony Orchestra (1997)
- Kansas City Symphony (4) (May 1998)
- Charlotte Symphony Orchestra (1999)
- Virginia Symphony (2000)
- Forth Worth Symphony Orchestra (2001)
- Puerto Rico Symphony Orchestra (2003)
(1) The Seattle Symphony became ineligible to remain a member of ICSOM during the 1988-1989 season, when it decertified its local and a majority of Seattle Symphony members ceased to be members of the AFM. back
(2) The Honolulu Symphony became the Hawaii Symphony Orchestra in 1994. The name was restored to Honolulu in 1996. back
(3) The San Antonio Symphony sent an observer to the September 1963 meeting at which bylaws were drafted and, having been present at a formative meeting, is listed in earlier bylaws as a charter member. However, San Antonio did not formally join ICSOM until 1968. back
(4) At the 1995 ICSOM conference, the Kansas City Symphony was ensured membership once it negotiated a union recognition clause into its contract. This happened in May 1998, and membership was immediate at that time. back
The Chamber Orchestra of Philadelphia was provisionally granted membership in 1968, and the orchestra's name appears in the Senza Sordino listing of orchestras that season. However, the orchestra doesn't appear again in the minutes, presumably because the orchestra membership did not subsequently confirm intent to join.
The Chautauqua Symphony was accepted as a member at the beginning of the 1979 conference, but the action was reconsidered a few days later. Although perhaps technically a member for that brief period, the Chautauqua Symphony has never been listed as a member and is not considered one in this compilation.
Several orchestras retained membership in ICSOM during difficult periods of transition as members attempted to keep their orchestras extant: The Oklahoma Symphony, which folded following a long strike in 1988; The Oakland East Bay Symphony, an incarnation of the Oakland Symphony following that orchestra’s bankruptcy in 1986; the Denver Symphony, whose musicians formed the cooperative Colorado Symphony in the face of bankruptcy proceedings in 1989; and the Louisiana Symphony, which succeeded the New Orleans Symphony and was briefly an affiliate member of ICSOM.
Alabama (Birmingham), Atlanta, Baltimore, Boston, Buffalo, Charlotte, Chicago, Chicago Lyric Opera, Cincinnati, Cleveland, Colorado (Denver), Columbus, Dallas, Detroit, Florida Orchestra, Florida Philharmonic, Florida Symphony, Fort Worth, Grant Park, Hartford, Honolulu (Hawaii), Houston, Indianapolis, Jacksonville, Kansas City Philharmonic, Kansas City Symphony, Kennedy Center, Los Angeles, Louisville, Metropolitan Opera, Milwaukee, Minnesota (Minneapolis), Montreal, Nashville, National, New Haven, New Jersey, New Orleans, New York City Ballet, New York City Opera, New York Philharmonic, North Carolina, Oakland, Oklahoma, Oregon, Philadelphia, Phoenix, Pittsburgh, Puerto Rico, Rochester, Saint Louis, Saint Paul Chamber Orchestra, San Antonio, San Diego, San Francisco Ballet, San Francisco Opera, San Francisco Symphony, Seattle, Syracuse, Toledo, Toronto, Utah, Vancouver, Virginia, Winnipeg.