and this should include musics and similar in games (excluding stuff like sessional content)

if you sell a game you should have to have bought a license to use the music (and similar) in the game permanently (for given game sold, new sold revision can change what they contain but only if there isn't deceptive advertisement and it's very clearly labeled that it's a different revision/the content changed!).

Single player games putting out "seasonal content" is kind of obnoxious too though so I wouldn't exclude them all. One example is the Moogle Chocobo Carnival and Assassin's Festival in Final Fantasy XV which players had to work very hard to patch back into the game after it was removed. The limited time Stellar Blade Summer Event wasn't nearly as impressive as the carnival, but it was still a black mark on a game that was otherwise refreshingly free from bullshit.