The two, high note and low note, are different. Back in the 1970's I had a 1974 Sebring with a single horn (standard fair) while my father had a 1974 Coronet with a single horn. Both sounded the same - like a sick cow. My 1978 Monaco had two horns and you could tell there were two separate pitches. My 1983 Imperial had three horns - sounded like a diesel locomotive horn.
Bill
Vancouver, BC