It seems that there's an inherent bug in the GoG build: every CD audio track begins with a second or two cropped from the music, and ends including the missing second or two from the next track. It's very annoying and disappointing.

http://www.gog.com/en/forum/little_big_adventure_series/music_has_aweful_compression_the_origional_was_pure_cd_audio/page1

If you take a look through this thread, someone uploaded a bunch of replacement tracks for the fudged-up rips included in the GOG version. They're high bit-rate .ogg versions of the tracks with the correct audio positioning. There should be instructions on how to replace them in the same thread.

The fact that GOG still hasn't fixed this is kind of ridiculous.