I can break out into song at any time while riding.

Manowar, Metallica, Polysics ect

When training on mountains its been

Ride up the mountain,
Ride up the mountain,
Ride up the mountain,

to the tune of ride of the Valkyries

Or I hurt myself today, Nine Inch Nails.

At the end of very long rides it always defaults into Hungry Man by Louis Jordan.