Forty years ago Michael Tilson Thomas could be found adorning the LP covers of pioneer recordings of American experimental music new and old. Reich, Cage, Ives, Carl Ruggles: they all passed under his fingers.

He still carries a torch for the American pioneers; this CD of Edgard Varese, Henry Cowell and Lou Harrison stems from an American Mavericks concert series with his San Francisco Symphony that toured the US this year. Cowell's compact Piano Concerto of 1930 stirs the most excitement. Clamorously dissonant, lashed with the composer's trademark tone clusters, wrapped in dense polytonal clouds, its mischievous exuberance is childlike and endearing. Jeremy Denk, the gifted soloist, dismisses the work's technical difficulties with ease, as does the trumpeter who begins Cowell's Synchrony with a sinuous three-minute solo, hot as moltern lava.

More arresting sounds follow from Cowell's pupil Harrison. His 1973 Organ Concerto is no work for a cathedral, but it would be right at home in Java or at a California beach party. The organ's jabbing chords come meshed with rattling and bonging from a gamelan-flavoured percussion ensemble. Very infectious, this; refreshing, too, with a delicate, musing central slow movement to allow mopping of foreheads. Paul Jacobs's delivery of the organ part is deliciously clean and bouncy. In Varese's intoxicating celebration of new horizons, Ameriques, Tilson Thomas drives his orchestra through the teeming sounds with tremendous vigour.