R_Pegio wrote:... I may have to stop playing because of a nagging ache to my left shoulder which is definitely induced by playing the guitar.
Sorry you're going through that. That's hard.
Some good ideas so far.
before you stop playing, consider...
1) when the shoulder hurts, lie on your back while practicing. I've done it and I liked it!
2) when sitting, some of the time rest the guitar on the right leg instead of the left to change the physical "geometry". Philip Rosheger and Jose Tomas (not to mention Paco de Lucia) sat that way. And they were quite fine guitarists.
3) increase your fitness level, especially shoulders and abs. This is what worked for me when I had a similar issue. I'm not talking about macho bodybuilding... 5 lb dumbbells and easy ab exercises for a few minutes a day. Easy to research online, create a balanced ex program, and try for 3 months to check. IMO, that would be a good thing for any guitarist, actually, shoulder pain or not.