There was an error in the data prep in many NES games that caused them to reverse the bit order of samples. Or more accurately, the games encoded the samples correctly, but the flaw is in the NES sound hardware.
The result is, many games with samples sound notably worse than they should. The most infamous example of this is the sound in Double Dribble, which sounds particularly bad on its title screen. The difference can be heard on the game’s page on The Cutting Room Floor. There’s a hack for Double Dribble on romhacking.net that corrects the samples in-game.
Another game this affects is the unlicensed Tengen NES game KLAX. In the arcade KLAX had very little music, but the NES version has excellent music that relies heavily on sampled instruments. There’s a fixed patch for that game on romhacking.net, too!
