I watched this movie a a young child, perhaps 4-6 years old. I was born in 1994, so the movie must have come out before 2000. The movie stars a young boy in a strange land. In one of the scenes he is being chases and taunted by a small black creature that even summoned musical notes to crash around the kid.
However, the creature is more mischievous than malicious, as I remember he was among the many friends that came in the end to help the kid defeat the actual villain.

Visually I remember the creature looking remarkabley similar to the shadow heartless in the video game series Kingdom Hearts.

https://vignette.wikia.nocookie.net/kingdomhearts/images/e/ea/Shadow_KHIII.png/revision/latest?cb=20190213051445

Two possible movies that have been brought to my attention are Little Nemo In Slumberland, and The last Unicorn. Although they are around the right time period and have a similar story, I could not find any of the scenes I remember in those movies.

The movie was animated in color and was in english.