What is a ballad rhyme scheme?

Ballad rhyme often uses four-line stanzas, with common rhyming patterns being AABB or ABAB. Stanzas can have four, six, eight or even a dozen lines, depending on the intent of the writer, how he/she wishes to express him/herself, and where the expressive emphasis lies. The ballads of Australian bush balladeer A.B. 'Banjo' Paterson vary in length.