I would assume that an external HDD needs power like any drive would unless it receives it’s power through the USB cable itself which I think is unlikely.
The capacity of the drive is probably too big to read as well.
I would just get some 32Gb SD cards or USB sticks and do it that way and still holds plenty of music 🙂
Not sure if 64Gb would be compatible.
A standard platter drive will also get hot without cooling, so if you are set on a hard drive, if possible, I would be using a SSD as a standard hard drive will not like all those bumps in our roads either.