Opera The Mother of Us All; Four Saints in Three Acts Trinity College Opera Group at Spitalfields Market Opera, London

A good modern opera needs a good modern libretto, and I know what a good modern libretto needs: strong characters, clear narrative, concise action. Or so I thought until last week, when I saw Trinity College Opera Group's stagings of two works, The Mother of Us All and Four Saints in Three Acts, by Virgil Thomson, whose centenary year this is. Gertrude Stein (who died 50 years ago) wrote the librettos for both operas and, as you'd expect, she presented character, narrative and action at an oblique angle, if at all. Yet far from rendering the operas null, her sly and eerie texts work in perfect counterpoint with Thomson's skewily idiomatic music.

Four Saints was premiered with an all-black cast in February 1934; The Mother of Us All in a Columbia University production in May 1947. The fact that both casts originated outside the opera house indicates the vitality Thomson wanted from his performers. Conventional bel canto here matters less than clear diction and rude energy. There was plenty of the latter in the Trinity College productions, but I can't say that Stein's texts were always sung with perfect clarity.

Stein herself was not particularly musical, once writing that "I came not to care at all for music, and so having concluded that music was made for adolescents and not for adults and having just left adolescence behind me and besides I knew all the operas anyway by that time I did not care anymore for opera." Maybe there's a lesson here for those in search of "Contemporary Opera That Works" - namely, that the ideal librettist doesn't like opera, and so doesn't want to write the perfect opera libretto but merely to provide functional text.

Trinity College staged the two works, on consecutive evenings, at Spitalfields Market Opera. The building has a provisional quality that is curiously attractive: outside, a five-a-side football pitch; inside, no stage, no pit, just a large space waiting to be filled with opera. Both productions managed that, although Emma Jenkins's staging of The Mother of Us All at times had rather too much of the end-of-term jape about it. Leah Hausman's more carefully choreographed Four Saints worked better: a passing reference to "St Nelson" Mandela was gratuitous, but generally the staging was well judged, and the repeated convulsions of laughter that seized the audience acknowledged the cast's greater success in getting the text across.

That's perhaps surprising, since the orchestra for Mother was a compact sextet, while Four Saints demanded 26 players. The latter's combination of trombone, accordion and harmonium produced a rugged churchiness, tunes and timbres emerging and merging with riotous abandon. Both scores fashion a workable modern idiom from elements that familiarity has never quite debased: church tunes, street songs, children's doggerel, patriot hymns.

Conducted by Nicholas Kok (Mother) and Gregory Rose (Four Saints), these productions gave us a bracing shot of American Modern, and the student casts clearly had a great time. College productions are fine things, and Trinity is to be congratulated for its enterprise; but, in these opera- saturated times, the audiences were not large, and large audiences are precisely what Thomson and Stein deserve.

n Robert Wilson's new Houston Grand Opera staging of 'Four Saints in Three Acts' is at the Edinburgh Festival, 29-31 Aug, Playhouse, Greenside Place. Booking: 0131 225 5756