These expressions are sometimes confused.
Besides usually adds: it is like saying with, or plus (+).
- Besides the violin, he plays the piano and the flute. (He plays three
Except subtracts: it is like saying without, or minus (-).
- I like all musical instruments except the violin.
Apart from can be used in both senses.
- Apart from the violin, he plays the piano and the flute. (= Besides the
violin … )
- I like all musical instruments apart from the violin… except the violin.)
After no, nobody, nothing and similar negative words, the three expressions
can all have the same meaning.
- He has nothing besides/except / apart from his salary. (= He only has his salary.)