Michael Tilson Thomas’s achievements as a composer have often fallen under the radar when measured against his many successes on the conductor’s podium. If nothing else, this definitive four-disc collection containing 18 works that span five decades, nearly five hours of music, comprising a substantial set of booklet notes, and containing some excellent performances by the San Francisco Symphony and New World Symphony orchestra, will do much to reaffirm Tilson Thomas’s creative legacy and importance.

Inevitably, perhaps, one is encouraged to draw comparisons in the orchestral works between MTT’s own style and the composers whose music he has championed over the years. The overture-style Agnegram for orchestra, originally composed in 1988, harnesses the energy and impact of Leonard Bernstein’s symphonic music (MTT’s mentor) to the polystylism of George Rochberg and David Del Tredici, while the open harmonies and extended lines in Street Song, for symphonic brass, suggest Copland.

These larger works on ‘Grace’ are occasionally interspersed with shorter songs for voice and piano, such as ‘Not Everyone Thinks That I’m Beautiful’ and ‘I’m Nobody! Who Are You?’ (the latter in a balanced duet between voice and viola), which reveal a different side to MTT’s creative personality: one steeped in the jazz, Broadway and Yiddish traditions inherited from his father, Ted Thomas. These influences combine to humorous effect in Symphony Cowgirl (Lisa Vroman hilariously hamming it up on this recording from 2001), while the funky Urban Legend – originally a concerto for contrabassoon and orchestra but presented here in a far grittier and punchier reincarnation for baritone saxophone – gains much from Pat Posey’s edgy performance.

At other times the impact of these influences can be startling and sobering, as in the melodrama for orchestra and narrator From the Diary of Anne Frank, where an idyllic world presented during the opening part soon descends into darkness and despair via goosestep-style mocking rhythms, snarling motifs and jagged, jarring dissonances.

Not all references emerge from the wellspring of the American musical tradition, however. Notturno, for flute and orchestra, invites comparison with Debussy’s Prélude à L’après-midi d’un faune, the work’s lyrical qualities vividly captured by soloist Paula Robison, while the propulsive Island Music, for percussion ensemble, draws inspiration from Balinese gamelan. The most powerful moments nevertheless belong to the several large-scale orchestral songs that feature throughout ‘Grace’, such as Meditations on Rilke, Whitman Songs and the Barber-esque Poems of Emily Dickinson, the latter featuring a superb performance by Renée Fleming made in 2002.

For listeners whose musical lives have been inexorably shaped by MTT the conductor (and I count myself as one of those), perhaps it’s high time we should be giving MTT the composer the respect and consideration that he deserves.