The five-note musical signature introduced with McDonald's “I'm Lovin' It” campaign is “ba da ba ba ba.”
The vocalized phrase functions as a sonic logo: a short piece of sound that can identify a brand even when no logo or company name is shown. McDonald's placed it at the end of many advertisements, where repetition helped audiences associate the notes with the restaurant.
People sometimes treat “I'm Lovin' It” as the entire sonic signature, but the slogan and the five-note vocal tag are separate parts of the campaign. The English words communicate the message, while “ba da ba ba ba” supplies the memorable musical ending.
The signature was introduced in 2003 and became especially useful for international branding because musical recognition can cross language barriers. Advertisements could be localized while retaining the same recognizable closing sound.