Hi - I am wondering about what exactly is the writer's share.

Say you start tow write for amusic library. You are offered a 50/50 split of the sync (usage license), Ok, that I get. But what is the writer's share? I have seen people ssay on this and other forums never ever give this up, but why?

Say you write a track for a library. A client of the library decides to you use your track in a tv show one time. They pay the library $4,000. Assuming there is no overhead and fees that need to be first recouped by the library - the library keeps $2,000 and sends you $2,000 - that is the 50/50 split, right? Ok, so again, what is the "writer's share"? I guess this confused me a bit:

Music Publishing - An Introduction (Part 2)

"With the exception of print music, income from musical compositions is generally split on a 50/50 basis between the music publisher and writer. The publisher's half of this income is called the "publisher's share," and the writer's half is the 'writer's share.' "

That would mean to me that the $2,000 the composer got in the above example IS the writer's share, is that wrong? Then what if the library offers 50/50 on the sync/usage license, but 75/25 of the writer's share - if the 2nd 50 is already the writers share?

If someone could kindly take a moment to explain this, I would appreciate it.

Also: when you write for a library, do you need to become a member of ASCAP, and/or BMI?

Thanks a bunch!