Using Two Laptops on the same iTunes account.

I currently use my 11 year old MacBook Pro for all my pictures and music, I have just purchased a new MacBook Air M4 and did not want to sync my photos and Music to it so not to fill up the storage.

I have added a few GarageBand MP3's to the MacBook Air but iMove cannot see them when I try to import them. They play OK, but just wondered is it because I haven't synced my iTunes from my old MacBook Pro?

Hope this makes sense ?

Cheers