piano- you can also sit with a smooshy pillow under your arm to support it...one that won't compromise the circulation yet offer support. lots of us do that. the microbeads make it so there are not direct pressure points. I think memory foam would offer a similar advantage.

here is one i found at amazon. they also can be found in Target in the automotive department (sold as driving pillows) and probably other places.

http://www.amazon.com/HoMedics-Homed...679678&sr=1-13