'mostly moral' indeed
This thread is really wierd. I can't understand people using drugs to stop their hands shaking in performance. Here, I think, is the moral issue: Beethoven's hands shook for his first public performances. I Guarantee that. Bach felt nervous when he first played for an audience. Paganini felt his technique slipping as a result of nervousness leading to shaking hands. My point here is that shaking hands is normal, for the first year or so of regular (as in once every couple of months) public playing. Its something you overcome. Everyone is different and everyone overcomes them in their own way.
HOWEVER, my main concern is not the above one, but this: the use of drugs to forcably control normal and healthy nervousness may not have obvious health-risks or any negative side-effects on the body at all. However, there is one very negative side-effect in my opinion: the nervousness which causes adrenalin to run through you before a recital, causing your hands to shake , could arguably have a very POSITIVE effect on performances. Think about it. Practice differs from performance how? First and foremost, practice consists of private, intimate study - NO ONE watching you. Performance is similar, with the addition of an 'audience' - people watching you. Why do you think you make less mistakes in practice than in performance? obvious isn't it? But then, once the nerves assosiated with public performance are mastered - thru practice and experience and NOT with drugs - what remains in public performance? only slight nervousness and adrenaline - a feeling of excitement in the performer that will lead to EXCITING PLAYING! Mark me well - this is why 'live performances' by the best leading artists ALWAYS produce more exciting playing than heard on recordings (which are bassically like practice with a microphone). This is why reccordings of live music are even made! Listen to the Sophia Recital, arguably one of the best recordings ever made of classical music - and a LIVE recording. Artur Rubenstien said on nerves "I go to the concert with the feeling of [a] little heart beating - 'do I own the piece or not - what will happen?' But this 'what will happen' is all for the good".
The moral issues exist, and Huxley saw their implications (see 'Soma'), but the main issue is that people who in any way chemically calm their nerves or adrenalin (and thats what Beta Blokers do) hurts only themselves, by skipping the developmental part of learning to perform for an audience. Their music will arguably remain dull and straightfoward and notes-on-a-page, because they will never feel the excitement of performance to the full extent.
Even if BB's only reduce the adrenalin slightly, isnt what your looking for 'the edge' in performance. Than surely NOT taking the drugs, and instead working WITH the adrenalin is the 'edge' you desire. Music is not a sport, but an art, and when 'performance-enhancing' drugs become accepted in performing art, artists will certainly not be 'the best they can be'.