The list of twentieth century piano trios may be short, but it contains several gems. One of the most precious is the brilliant specimen written by Maurice Ravel in 1914, shortly before he temporarily abandoned life as a musician to serve as a driver for the French army. The Piano Trio in A minor is a true sonata for three players, rich in the harmonic and textural innovations Ravel had accomplished in the prewar years, but ultimately, and very possibly more significantly (Ravel certainly felt so), composed around balanced, quintessentially Classical patterns.
The trio has four movements: Modéré, Pantoum (assez vif), Passacaille, and Final (animé). The first movement is a strikingly new variety of sonata-allegro form. The first theme, announced by the piano in pianissimo parallel chords at the very opening of the piece and then taken up by the strings in octaves, is like a shadowy recollection of something out of Basque folk music. Its unusual ostinato rhythm seems to echo in the mind's ear even after Ravel has moved on to the Plus lent qu'au début second theme -- a second theme that is very unusually set in the same key as the first. (Ravel makes sense of this atypically tonic-saturated exposition by ending the movement not in the tonic but rather in the relative major, C.) A brief development makes way to a truncated recapitulation which in retrospect seems but a preface to an extended coda in which the ostinato's first idea lingers in the lowest bass of the piano until at last it becomes a faint, colorless drone that dies away into nothingness. This is a remarkable movement that deserves its reputation as a masterpiece.
The second movement is a playful scherzo that will likely sound the most typically French to most listeners. The Passacaille is of course a passacaglia, taking a slow, winding eight-measure pattern as the material to be repeated; the repetition is not strict, and soon a second thematic notion worms its way into the movement, helping to build a massive climax.
Ravel's love of shifting meters is put on display in the quick-paced Final, with contrasts between 5/4 / 7/4. Again sonata-allegro form shapes the course of the music, seeping through the cracks of what might at first seem to be a more freely composed exhibition of instrumental passion -- and the closing bars, filled with shimmering, never-ending trills from the strings and a wild whoosh or two from the piano, are certainly passionate.