Firm and Fabulous
Like another reviewer, I chose this for use playing my instrument.  The cushion is very firm, but comfortable, and hardly compresses under my not inconsiderable weight.  I also tried the Jobri Seat Wedge which flattened out until it was a pancake, and the slightly firmer DreamFoamHD Orthopedic Coccyx Cushion, which also flattened out way too much, especially under my rear, which made it less of a wedge that it was when it wasn't under my bum.
Rating: 5 stars