Comment by Cthulhu_
There were two games that I remember had pretty good sound on the PC speaker, one was a golfing game which had like bird whistles and voices, the other was a 2d side scroller with voice acting, iirc it said "jesus is here!" when you picked up an extra life or something.
There was also Le Manoir de Mortvielle which had a speak synthesis throughout the whole game and a recorded music as intro, all on the pc speaker https://www.youtube.com/watch?v=GXB8AddxBgM