As aforementioned, you will need the matching sound ID to add an audio effect using the Roblox Studio Explorer window. In the case of the popular Osu hit (which is taken from the titular rhythm ...

Any new Kill Sound ID codes will be mentioned in the announcements channel of the Combat Warriors Discord server. Join the server and verify your account to stay updated on the latest codes.

Tallarico and Roblox seemed to work something out, as in 2020 it was revealed that the "oof" sound would be replaced but with the iconic version still licensable for $1 or 100 robux.