The Konami Morning Music played when you power on the machine and enters its countdown sequence for the bubble memory modules to heat to a good enough temperature for the machine to be fully operational
Reason for the countdown
As with Twinbee, the system this game ran on used bubble memory chips rather than the standard transistor-based ROM chips, so during the Power On Self-test (POST) sequence, the chips must be heated to a good enough temperature in order for the machine to read its game ROMS properly. Once the chips has finally been heated to room temperature, the game will proceed to its actual bootloader and then it's ready to be played.
Usage on emulators
Running Gradius on MAME or any other arcade-emulating programs/apps will cause the countdown to go too fast because the emulator runs on a hard drive/SSD rather than bubble memory because hard drives/SSD's don't require a long heat-up time to work right.