In the viola bastarda style, a polyphonic composition is reduced to a single line, while maintaining the same range as the original, and adding divisions, improvisations, and new counterpoint.

Francesco Rognoni, a prominent composer of divisions, stated that although works using the bastarda techniques could be played by a number of instruments, including organ, lute, and harp, the "queen" of bastarda technique was the viol because of its agility and large range.

Rognoni's Selva de varii passaggi (Milan 1620) was the definitive treatise on viola bastarda technique.

[2] Viola bastarda music is written for standard viol tuning, in fourths with a third in the middle.

Early sources speak of the viola bastarda as a style of playing, and the ranges of pieces written during this time indicate that bastarda pieces were played on whichever size viol was at hand; however, Rognoni describes the standard size of a viola bastarda as between that of a tenor and bass viol, indicating a change in understanding of the term.