Trademark registration number 74485223.
Description of Mark: The mark consists of the exhaust sound of applicant’s motorcycles, produced by V-Twin, common crankpin motorcycle engines when the goods are in use.
It almost makes sense. You pay your hard-earned American dollars to get that distinctive Harley-Davidson sound. You don’t want some Southeast Asian company copying it into their rice-burners. It seems that the USPTO operates only in the visual mode.
If Harley-Davidson had called the sound of a V-Twin “music” they could have copyrighted it and collected royalties. I think I’ll send them an email.