In several of the Castlevania games you'll find that the developers threw in remixed versions of some songs from prior titles, which is fine, lots of those songs were pretty good.
But occasionally they're a little harder to find than others. Like in Castlevania: Bloodlines.
You have to first go to the Options Screen
And play Song #5 and Sound Effect #073 (and leave those two selected as you exit the screen)
Then, start the game and progress until you get the "4th powerup" for your guy (an orb for John and a book for Eric)
Once you do, you'll be greeted with a song from a classic Castlevania game! But probably not the one you're thinking of. The song that's played is from the opening stage of Castlevania III, titled, shockingly, "Beginning".
Don't have a Genesis and a copy of this game handy? You're in luck! The remix can be downloaded here