This is a direct excerpt from Kurt Kalata's Hardcore Gaming 101 Page on Shin Megami Tensei. Just giving credit.
"Megami Tensei 2 uses a specially designed memory mapper that generates higher quality sound. The result is some of the finest sounding compositions on the Famicom, which are stylistically close to music in the Super Famicom games. This spells problems for non-Japanese gamers though - the game comes on a double size cartridge that won't fit in a standard NES, and the music wouldn't work right anyway, due to differences in the Japanese sound hardware."
The question here is how to play games with these special cartridge chips. I guess a converter isn't going to work. What's the most cost-effective way to get to play Megami Tensei II (and Castlevania 3 Jap)? Only crazy Famicom guys are probably going to know about this, so if you don't know what I'm asking, don't fret. The only possible method I can think of is the FC Consoles people sell at flea markets and online.