When two or more people in a car sing a song in harmony.
When sang with the radio, these harmonies often sound spot on, but if they were to be sang without the backing track, they are usually wrong and out of key.
When sang without a backing track, the harnonies are more likely to be very good, or very bad, rather than just mediocre (as with the radio).
1. Dude, one the way up here me and my friends were listening to "By the Way" by the Red Hot Chili Peppers. Yeah, We got the Carmonies PERFECT!
2. My A Cappella group practiced on the way to the show. We sang in perfect Carmony.