Our keyboard player says that time sigs and tempos mimic and stimulate the heartbeat. IE when in the womb we hear our mothers heartbeat and changes in ITS rythm can relax us or excite and stimulate us. When we hear a piece of music it subconsciously reaches this retained memory affecting our moods and feelings. He says that many books and articles have been written on the subject. It is probably why music was invented and developed and why mothers sing lullabys and why we tap our feet etc etc. He might have a point.