Which US singer provided the voice of Charlie Brown's little sister in the animated Charlie Brown TV series of the mid 1980s?

Stacy Ferguson of the Black Eyed Peas:

1) "Kathy Steinberg was the first to voice Sally Brown in 1965. Various actresses had voiced her since. Lynn Mortensen voiced her from "It's A Mystery, Charlie Brown" (1974) to "Be My Valentine, Charlie Brown" (1975). In It's Flashbeagle, Charlie Brown (1984) and Snoopy's Getting Married, Charlie Brown (1985), and the 1985 version of "The Charlie Brown and Snoopy Show", Sally was voiced by Stacy Ferguson of the Black Eyed Peas. In It's Christmastime Again, Charlie Brown (1992), Sally was voiced by Jodie Sweetin from Full House.
Kristin Chenoweth played Sally in the Broadway revival of the musical You're A Good Man, Charlie Brown winning the Tony Award for Best Featured Actress.. (The character of Sally did not appear in the original musical; she replaced Patty from the original production, who had long since disappeared in the comic strip.)"
Source and further information:
http://en.wikipedia.org/wiki/Sally_Brown#Portrayals


2) "Stacy Ann Ferguson (born March 27, 1975), better known by her stage name Fergie, is an American pop/R&B singer, songwriter, and actress. She is a former member of the kids' television series Kids Incorporated, and the girl group Wild Orchid. Ferguson was also a co-host of the television show Great Pretenders. She is currently a vocalist for the hip hop/pop group the Black Eyed Peas, of which she is the sole female member, as well as a solo artist, releasing her debut album, The Dutchess, in 2006. The album has so far spawned three U.S. Billboard Hot 100 number one singles and five Top 5 hits, making The Dutchess the seventh album from a female artist to spawn five Top 5 hits"

"Ferguson was the voice of Sally Brown in two Charlie Brown specials: It's Flashbeagle, Charlie Brown (1984), and Snoopy's Getting Married, Charlie Brown (1985). She also voiced Sally in the 1985 version of The Charlie Brown and Snoopy Show."
Source and further information:
http://en.wikipedia.org/wiki/Stacy_Ferguson