Every released track is not one thing you own. It is two.
This is the single most important distinction in the whole subject. Get it, and everything downstream falls into place. Miss it, and every deal and statement stays confusing.
A released track contains two separate copyrights:
The composition, itself: the melody and the lyrics, independent of any particular performance. This is what a songwriter creates.
The master, the specific : the actual audio file that came out of a studio session. This is what gets pressed, uploaded, and streamed.
They are different legal works. They can be owned by different people. They are licensed in different deals and collected by different organisations. One song can have many recordings (a demo, a single, a live version, a cover) and each recording is its own , but they all share the same underlying composition.