The suggestion here is to go with Gail Ann Dorsey, David Bowie's bass player for teh last few albums / tours. Why? Well apart from being a fantastic bass player and singer, these are some quotes from here:

Gail Ann Dorsey: Early on, on the Outside tour, David asked would I consider singing Under Pressure like the Annie Lennox duet he performed at Freddie Mercury's Memorial Concert.

Gail Ann Dorsey: Queen is my favorite band of all time and I remember being so overwhelmed at David's suggestion that I cried.

Gail Ann Dorsey: To sing a part originally sung by Freddie Mercury so far has been the greatest honor of my life.