<p>It is possible to play some instruments more hours a day that it is others. The criteria is what is physically possible without incurring injury. In those instruments where 4-6+ hours a day is possible, the standards of excellence are very high. String and keyboard players are in the 4-6 category. Singers and brass players are more limited…I can only speak with absolute authority about singers, and for issues of vocal health they can manage no more than 2-3 a day (including ensemble singing) and ONLY if spread out wisely. It might be more possible for someone to manage a double major in voice and piano, for instance. I doubt a wind or brass player could double major in voice, because the mechanics of breath usage are different. Concerning ensemble playing: accredited BM degrees require a certain number of credit hours in ensemble. At the premier conservatories, orchestra assignments may be intermittent, not a constant part of the schedule. For keyboard players, ensemble assignments will include chamber music and collaborative playing (i.e.accompanying the singers and instrumentalists).</p>