As a pianist Mather has displayed a strong commitment to performing new music by himself and by other contemporary composers. He has performed in many major performance venues and music festivals, often appearing with his wife, pianist Pierrette LePage, in duo-piano works. The husband and wife team have also partnered on several recordings. He served as director of the Société de musique contemporaine du Québec from 1966–1981 and later served as treasurer.
Mather is a composer of orchestral, chamber, vocal, and piano works. A disciple of Ivan Wyschnegradsky, his music often employs microtonal scales. Though he was distrustful towards microtonal music after hearing Alois Hába's works, his meeting with Wyschnegradsky in the seventies was crucial for his aesthetic and his use of microtonal scales. As a pianist, he and his pianist wife, Pierrette LePage, have performed many of Wyschnegradsky's pieces.
As a composer Mather employs Wyschnegrasky's principle of non-octavic spaces. He wrote many works using this technique, notably in his Poème du délire (Poem of Delirium), a tribute to Alexander Scriabin (as a reference to his Poem of Ecstasy and Poem of Fire) who influenced both Mather and Wyschnegradsky. Mather's compositions are also strongly influenced by his love of poetry and wine.
Works
Stage
La princesse blanche (opera), 2 sopranos, baritone, bass, small orchestra (16 players), 1993
Madrigal II (text by Hector de Saint-Denys Garneau), soprano, alto, flute, harp, violin, viola, cello, 1968;
Madrigal III (text by Hector de Saint-Denys Garneau), alto, harp, piano, marimba, 1971;
Madrigal V (text by Hector de Saint-Denys Garneau), soprano, alto, small orchestra (17 players), 1973, revised 1980;
Au château de Pompairain, mezzo-soprano, orchestra, 1976;
Musique pour Champigny, soprano, mezzo-soprano, alto, B-flat clarinet, French horn, harp, piano, percussion, 1976 (Winner, Jules *Léger Prize for New Chamber Music, 1979);
Les grandes fontaines (text by Anne Hébert), soprano, piano, 1981;
Un cri qui durerait la mer (text by Marie France Rose), bass-baritone, piano, 1985;
Travaux de nuit, baritone, piano, 1990 (also arranged for baritone, orchestra, 1990);
Des laines de lumière (text by Gatien Lapointe), bass-baritone, 2 quarter-tone pianos, 1996;
La voix d'oiseau, coloratura soprano, piano, 1998;
Trois Poèmes de Gatien Lapointe, voice, piano, 1998;
Onze Poèmes pour la main gauche, soprano, piano, 2000