yeah but when they march, they typically have someone keeping time. When trained to march, you always have someone singing to keep that time! AROC normally does it. They drill for particular times. They almost certainly did not drill for these songs. They probably weren't told.
So in order to march to a time, you have to know what time you're marching to, which means you'll probably also need to know a little bit about music! When you don't have someone screaming the timing to you you now have to GUESS. And everyone has to guess independently. And some will be wrong.
Have definitely heard the singing - I wonder if they were told not to sing while the music was playing. What does AROC stand for? I could only find Army Requirements Oversight Council, but that seems a little to back-office for this context.
Assistant Recruit Chief Petty Officer, said AROC, but actually spelled ARCPO. It doesn't mean anything outside of basic, they just pick some competent people, one to be the recruits' 'leader,' and another to be the assistant to them.
Thanks!