No rotator cuff injury. That was a close call. I got a second opinion from a physiotherapist. Good move on my part. These arms need to last at least another decade of professional music making, maybe even 15 years. That's a lot of $$$ on the line. No time or place for screwing around or fooling myself.
I'm happy to report that icing and stretching is doing the trick.
What's the take away from this experience?
Drummers upper body workout: http://drummagazine.com/a-drummers-upper-body-workout/
How injuries occur in playing the piano: https://books.google.ca/books?id=43wThWiJe20C&pg=PA142&lpg=PA142&dq=pianist+fitness&source=bl&ots=7FIADFgF6p&sig=PtZqL0mANnwtxEEbTBggRsGbXZY&hl=en&sa=X&ved=0ahUKEwiR-63j5vfQAhVP_WMKHUrWDe0Q6AEITjAI#v=onepage&q=pianist%20fitness&f=false
David Story: Professional pianist, drummer, composer, and educator. Well into his 4th enthusiastic musical decade, David works with adults pursuing musical dreams in the autumn of life, while he maintains an active presence in the Toronto arts scene.