Regular music missing from some levels

I've played the original game back in 1997, and I initially thought that it was my impression that some music were missing from some levels, but i confirmed recently playing on a retro PC and also from some gameplays from YouTube: Level 4, was supposed to play Track14 and 15 (as level 3 does), but it only plays the 15. Level 8, was supposed to play Track16 and 17 (as level 6 does), but only plays the 17. Level 17 (light and dark side), was supposed to play Track25 and 26, but only plays the 26. Level 19 (light and dark side), supposly plays Tracks 25 to 27, but only plays 26 or 27. PS. Level 10, according from some YouTube videos (probably using the GOG or Steam version of the game) begins with Track22. But i don't quite recall having it in this level.