1. A scheme first found in the opera arias of the mid-eighteenth century (A-B-A-B-coda). Unlike the abridged sonata form (slow movements) it is distantly related to, there is no tonal principles within this form.

2. A means of shaping the form of a musical work developed by Witold Lutosławski and typical of his style. The piece is comprised of two segments, the first of which is an introduction of capricious character and frequently-interrupted development; the second, on the other hand, develops in a more decisive, continuous manner, leading to a culmination. In Lutosławski’s works, the clear contrast between the two movements is served by the mutual opposition of the ad libitum techniki dominant in the first movement and the traditional playing at a tempo common to all of the musicians in the second. Bipartite form occurs – openly or otherwise – in most of Lutosławski’s works. It had a particularly strong influence on the form of his String Quartet (1964) and Symphony no. 2 (1967).