@aodoherty, I'm sorry, but I don't understand how this could be a problem with "the Sims 4 base with City Living", when @RandomBuzziness has tried to serenade with the piano in her game and was able to do this?๐ค . (Unless @RandomBuzziness doesn't have City Living... but she certainly has the Sims 4 base game! ๐) I would test this my self, But I have many save games and cant' find my level 10 pianist right now to test this with. ๐ข
I understand that you never had problems with any of your CC before, but that does not matter because the game was just updated a week or so ago. That means that any Mod or CC item has a chance of being outdated. You did test them, but did not follow the instructions and did them in reverse order. ๐ข I've never heard of anyone testing CC and Mods in that way, so we can't be sure that that way will properly test them. ๐ค๐
This is the way that Mod and CC experts and tech experts recommend testing:
1) Move the Mods Folder to your desktop
2) Delete localthumbcache.package file in the game folder.
3) Fix you game in Origin by logging in and go to Library, then right-click on The Sims 4 and choose the "Repair Game" option from the list. Wait until Origin finishes repairing all your packs and not just the base game.
4) Now, when you turn on your game again, it will create a new mods folder that will be empty. Check to see if your game is now working without mods/CC.
5) Now you can try adding back items from your Mods folder one at a time checking your game each time to see which item is causing your game to not work properly. If you have a lot of items, you can try the 50/50 Method.
If you add back an item and check to see if your game works and it exhibits the same problem again, you know that it is that item that is outdated, and you can go to the creator of that CC item or Mod and see if they have an updated version that was updated after EA's latest patch to the game. Then if they do, download that updated CC item and replace it with the broken one! ๐
The only other possibility is that either your lot, one of your Sims, or that particular save is glitched/corrupted. Either @CGrant56 mentioned this possibility earlier, or else @RandomBuzziness did. And you are right in that older save games have more of a chance of developing problems due to file corruption. But it is still best to properly test your CC/Mods first to rule out that possibility, or to fix the CC/Mods if that is what is causing your problem.
I'm sorry if my instructions are not clear, or that I'm repeating myself. But you can't rule out CC/Mods without properly testing them, โน๏ธ I would really like to see you enjoy your game and be able to have your Sims use the serenade action with their pianos! ๐ค๐
Thank you for being patient! โค๏ธ