British Rules and Regulations from 1798 actively discourage the use of music for keeping a marching cadence in any circumstance, because it causes confusion along the line. Sound is relative to the observer and marching near hills or buildings is asking for trouble - I remember marching in city parades as a boy scout and hearing two different bands ahead and behind play different pieces on different beats, surrounded by skyscrapers, it was cacophonous to say the least. The manual permits the band to play for raising morale or putting on a jolly old spectacle though.
http://books.google.ca/books?id=I3pSJLInt5MC&pg=PA78The use of MUSICK or DRUMS to regulate the march is absolutely forbid, as incompatible with the just and combined movements of any considerable body, and giving a false aid to the very smallest -- They never persevere in the ordered time or in any other, are constantly changing measure, create noise, derange the equality of step, and counteract the very end they are supposed to promote. The ordered and cadenced MARCH can be acquired and preserved from the eye and habit alone, and troops must by great practice be so steadied as to be able to maintain it, even though drums, musick, or other circumstances should be offering a different marked time. -- On occasions of parade and show, and when troops are halted, they are properly used and when circumstances do not forbid it, may be sometimes permitted as inspiriting in column of march, where unity of step is not so critically required. But in all movements of manoeuvre whatever, and as at any time directing the cadence of the step or in the instruction of the recruit, officer or battalion they must not be heard
Synchronization was meant to be by eye, not ear. Light is faster than sound after all, and less prone to distortion.
Interestingly, in later additions of the manual, this passage is preserved almost verbatim but is moved to the section about wheeling in file, which makes me wonder about how universally its wisdom was applied.
