"Payday March" is a

bugle The bugle is one of the simplest brass instruments, normally having no valves or other pitch-altering devices. All pitch control is done by varying the player's embouchure. History The bugle developed from early musical or communication ...

march March is the third month of the year in both the Julian and Gregorian calendars. It is the second of seven months to have a length of 31 days. In the Northern Hemisphere, the meteorological beginning of spring occurs on the first day of March ...

. The first strain, repeated, also serves as "Pay Call", a bugle call to announce that the troops will be paid. :

References

bands.army.mil
Bugle calls {{music-instrument-stub