Sonata for Flute and Piano was commissioned by Jeanne Baxtresser, former principal flautist of the Montreal and the Toronto Symphony Orchestras. She premièred the sonata with Jane Coop at the piano in the first season of the Parry Sound Music Festival, August 9th, 1980. It has been performed since by a number of flautists in Canada and in several European countries.

The first movement is an Allegretto in ternary form, but as in most compositions by Morawetz the recapitulation of the opening themes employs new textures and colours. The playful first motif in its second statement has a very dramatic feeling while the equally gay second theme appears at the end of the movement in a slow pensive mood.

In the slow second movement heavy chords in the piano introduce the first theme. The flute follows, starting gently, almost unaccompanied, but gradually growing in strength and expression. Later the opening bars of the piano are brought back but this time as a background to fast-moving passages in the strong high register of the flute; a cadenza-like interlude in the flute, with many grace notes preceding all accents, slowly descends from the high fortissimo notes to a soft low C-sharp. The following quiet coda derives its thematic material from the flute melody at the beginning.

The last movement is a lively and sparkling Allegro. Its structure can be described as a free sonata form. The first theme is gay in various meters. The second theme starts with two bars in the piano in the style of a comfortable valse, suddenly interrupted in the following two bars by an "impertinently protesting" motif in the flute. The development is based exclusively on the first theme and therefore Morawetz starts the recapitulation with the second theme in a brilliant climax. After a diminuendo, the coda starts softly but builds quickly to an exuberantly happy and animated ending.