The question is if it isn’t completely sufficient if this information is available in the project page.
If you then want to list the projects that belong to a given artist, you can filter the projects by artist.
This way you can still have your many-to-many relationship but without having to duplicate the relations.
If you still want to do this, you can use hooks.
When working with relationships, I’d recommend using the AutoID plugin to give each page a unique key that is then stored as reference (foreign key). This is necessary to make sure that the reference to the page is still valid in the future, even if the referenced page is later deleted.