Actors may seem to be natural subjects for stage or film biographies, but only if their lives are colourful and/or tragic. At least, in the case of musicians and singers, film and stage can illustrate the work and exploit its popularity. In the theatre, Jean-Paul Sartre gave his own slant to Edmund Kean; George S Kaufman and Edna Ferber portrayed the Barrymores as The Royal Family, in their 1927 comedy; and Arthur Miller wrote about his marriage to Monroe in After the Fall. There was also the musical Judy, about Judy Garland.

Musicians were an early discovery of film-makers: Michael Curtiz, director of Casablanca, did lives of songwriters George M Cohan in Yanky Doodle Dandy (1942; with James Cagney) and Cole Porter in Night and Day (1946; with Cary Grant), and jazz musician Bix Beiderbecke in Young Man With a Horn (1960; with Kirk Douglas). Swing was celebrated in The Glenn Miller Story (1954), and there was soon a rash of rock'n'roll movies, including the hilarious Tommy Steele Story (1957), with the Bermondsey boy playing himself; and all those films where Elvis played a singer unlike himself.

Singers tend to have more potential as film subjects when they are women and their lives were miserable: Billie Holliday, for example (Lady Sings the Blues, 1972; with Diana Ross) or Karen Carpenter (Superstar, 1987). There are no films about Charles Trenet or Maurice Chevalier, but two about Edith Piaf: Guy Casaril's Piaf (1974) and Claude Lelouch's Edith et Marcel (1983). The lives of tragic female film stars are equally ripe for biopics. Of course, there are several of Marilyn Monroe (The Sex Symbol, 1974; Goodbye Norma Jean, 1975; Marilyn the Untold Story, 1990) - though none worth watching; and, inevitably, after her daughter's revelations about her irrational behaviour, Joan Crawford got the treatment in Mommie Dearest (1981, with Faye Dunaway). The actress Frances Farmer would probably have been forgotten were it not for her struggle with drugs and mental illness: Jessica Lange and Sheila McLaughlin played her as feminist martyr in (respectively) Frances (1982) and Committed (1983) - the last as in "mental institution".

In a sense, films and plays are part of an actor's biography: George Cukor's A Star is Born (1954) seems inextricably tied into Garland's tragic life and there is more than a bit of Funny Girl in Barbra Streisand - even though the picture's heroine was in fact the actress Fanny Brice, star of the Ziegfeld Follies. Tragedy and sleaze are not the only things that attract film-makers; period atmosphere can also carry a biopic, as in Karel Reisz's Isadora (1968; with Vanessa Redgrave), Richard Fleischer's The Incredible Sarah (1976; with Glenda Jackson as Sarah Bernhardt), Ken Russell's Valentino (1977; with Rudolf Nureyev), and Richard Attenborough's Chaplin (1992). But in reality many actors possess quite dull personalities, and it may require a spot of tragedy, addiction, mania or sexual deviance to make their lives worth filming. Robin Buss