It applies 70 years after the death of the author. After that, the right automatically passes to the heirs!
Intellectual property therefore never becomes the property of the general public, which is why heirs of great compositions still earn money from them.
I am not a lawyer, but I think you have stated it incorrectly: copyright is limited in time and if the holder dies before the expiry of the protection period, it passes to his heirs. A conductor is acknowledged to have had a creative influence on his concerts; therefore, there are still rights on the Karajan concerts – but anyone can use the Mozart melodies as ringtones for mobile phones without obtaining licenses.