Castlevania 1 sound byte found

I tried this as a favor for someone else. In Castlevania on the NES, byte 7F6 will affect the next sound played. For example, setting it to 2A will play Vampire Killer. The next two or three are just a specific channel, such as square or triangle or noise, for that song.

To make playing the songs easier, set byte 25 to FF. This is the timer for the Konami logo at the start. So reset your emulator and whatever sound you have 7F6 will play during the Konami logo until you reset the emulator again.