This is what we found on Wikipedia regarding the Motown On the Rocks:

Fanny was an American rock band, active in the early to mid 1970s. They were one of the first all-female rock groups to achieve critical and commercial success, including two Billboard Hot 100 Top 40 singles.

The group was founded by sisters June and Jean Millington (on guitar and bass respectively), who had been playing music together since they moved from the Philippines to California in the early 1960s. After playing through several variations of the band, they attracted the interest of producer Richard Perry who signed them to Reprise Records in 1969 as Fanny. The band recorded four albums together before June quit the group, leading to the original line-up splitting. Following a final album, Fanny disbanded in 1975. The Millington sisters have continued to play music together since the split, and with a former drummer, Brie Howard-Darling, formed the spin-off group Fanny Walked the Earth in 2018.

The group attracted critical acclaim for rejecting typical girl group styles and expectations of women in the rock industry, instead emphasizing their musical skills. Later groups such as the Go-Go's, the Bangles, and the Runaways cited Fanny as a key influence.