 One objection is that this mereological account of the relation between sounds and sources cannot account for hearing ordinary objects by hearing their sounds. You could not strictly hear a tuba by hearing its sound because a tuba is not an event of which a sound is a part. However, the sound is part of the event of playing the tuba, and the tuba is a participant in that playing. So, though you are not aware as of a tuba, you are aware as of an event that involves a tuba. That perhaps is enough to explain talk of hearing tubas and to assuage the worry (for further discussion, see Young 2018).