By changing the way we perceive the world. For example, in experiments in which people looked at smiley or sad face icons, the music they were listening to affected what they saw. Even a neutral face could be judged as happy when listening to happy music. Music also stirs up old memories without us intending it to, often bringing back emotions experienced at the time. The rhythm or beat of music causes all sorts of bodily responses including tapping fingers and feet. A beat can even affect our heart rate and, when people sing together, their breathing may become synchronised and positive emotions increased. These effects are perhaps not so surprising when we know that musical patterns affect the auditory brainstem, as well as the auditory cortex, parts of the neural reward system and other areas involved in memory and emotion.