Basically, it's promised to be a fun kids' movie, with conflicts hinging mainly on sofa-ruining. And it is! At least until the final act.
The Horrifying Scene:
Beethoven actually has a villain: an evil veterinarian who conducts illegal experiments on animals. The vet becomes obsessed with kidnapping Beethoven, and even goes so far as to orchestrate a fake bloody attack so he can confiscate the enormous beast.