Some days ago, while listening to some of the Zelda II soundtrack, I noticed something - it's possible you may have noticed it too. Zelda II's soundtrack sounds inherently different from the original Zelda. And not just due to the composer, either - (Koji Kondo in The Legend of Zelda, while Akito Nakatsuka did the music for Zelda II: The Adventure of Link in his only Zelda compositional work. Interested readers may like to know that his Dungeon Theme from the game was used as the StreetPass Battle Theme in The Legend of Zelda: A Link Between Worlds. Rather the remix [as it is now orchestral] was done by Nakatsuka himself or the game's composer Ryo Nagamatsu is unknown, but I am of the opinion that it is the work of Nagamatsu as Nakatsuka does very little compositional work these days.) -it sounds like it's using different 8-bit 'instruments' from the original Zelda.

A portion of this may be down to the technique of the composers. I however and of the opinion that this down to the sound programming - in particular, the sound driver used. You see, in these early days of gaming, there was no standardized software. Composers were often also proficient programmers, so each composer might program his own sound driver. Of course, you'd get the rare occasion where a programmer would have to do the music as they couldn't afford a composer, but we do not speak of these.

I did some digging at this website for information, having stumbled upon it months ago and remembering a mention of sound drivers. And with that - success! Nintendo used three sound drivers on the NES. The first was programmed by Hirokazu Tanaka (at the time he started working at Nintendo, there was no sound driver for the Famicom, so he programmed one himself), the second by Akito Nakatsuka (initially he used Tanaka's before programming his own around 1986.) and the third by Koji Kondo (Nintendo required its main composers to write their own sound drivers, so Kondo did likewise). It is safe to assume that Kondo used his own sound driver for his Zelda music, thus, given the different sound of the Zelda II soundtrack, one can only guess that Nakatsuka likewise used his sound driver for Zelda II's music.

A mystery solved. But one does wonder: what games had what sound driver? Kondo's (and possibly Tanaka's and probably many, many other company's sound drivers) fit the definition of 'classical' 8-bit music. Nakatsuka's doesn't. Metaphorically, it's the sitar to Kondo's pizzicato violin. Going off of only the Zelda game's, Nakatsuka's is immediately different from the first Zelda, and thus, Kondo's driver. One further distinction is that his driver seems peculiarly weak at the higher pitches, as the Zelda II title theme shows off.

Something to wonder. Perhaps one day we may know, either through guesswork or someone managing to get their hands on information straight from the Yoshi's mouth.