Well she can play piano, but boy oh boy can she sing and it is easier to just belt them out then to do both. I heard she learned how to play piano by ear but on the other side her mother was suppose to be a very good piano player before she died and she probably learned some from her mom early.
There is also the little added awesomeness that she was good friends with Dionne Warwick & Cissy Houston*; so Whitney Houston grew up calling Aretha & Dionne Aunts.
Cissy by the way can really sing, I think she was better then her daughter.
This is probably too rock for this thread but I'll link to her anyway. I understand this is the most covered song of all time, Cissy gives it a lot of Gospel.
Another Folk-Rock song made Gospel by Cissy: .
* who I ran a stage in Red Bank for her once in the 90s for a Jazz & Blues Festival.