Battle Commands

Had a little look around and so far my findings seem to suggest that there is very little information on this topic.  Some sources suggest use of music instruments (horns, drums, bag pipes etc..) as well as waving standards or simple hand, sword, or shield movements combinations were more preferred (especially in large battles)  than actual voice commands. Main reason for it being too noisy on a battlefield.

"The first thing is that almost without exception, in c15th England at least, when battlefield commands are being relayed they are in the most simple terms and involve the Standards and trumpets.
To paraphrase 'they sounded their trumpets and advanced the standards'....So the first point is (in England) that I believe that the trumpet is the primary martialing vehicle.

There are numerous Medieval books on Hunting (Gaston Phoebus and The Master of Game being only two). Most of these detail very specific trumpet calls to signal the different stages of the hunt (chase, recall, the kill etc. etc.) Most are variations on a theme and work like a Morse code (using patterns of long and short beats rather than varying the pitch of the note)."

More info can be found on FireStryker Living History Forum  Historical Combat, Tactics, and Techniques thread