My husband and I have a secret weapon that we use for in-car whining. It's a magical cd that starts with Pachelbel's canon and includes such baroque classics as Bach's Jesu, Bleibet meine freude and Adagio by Albinoni.
It is guaranteed to calm any one of our three children when they are tired and whining and crying. If it doesn't work then we just pump up the volume until the child in question can hear it over their crying and we put the volume back down as the child quiets and lets the music wash over them.
The two older kids are like Pavlov's dogs in the back of the minivan... the first few chords of the canon have them silenced and leaning back into their car seats. By the crescendo near the end of the piece they are usually asleep (and often drooling!). The baby is well on her way to being trained by the music as well, so we are three for three with this most wondrous cd.
Do you have a magical child-calming trick?