In this review I present studies concerning the processing of music in the brain. The aim of the review was to identify neurobiological mechanisms underlying music therapy effects, with special focus on music used for pain relief. One of the main challenges in the field of music therapy seems to be the lack of a common theoretical framework for the diverse music therapy working areas and practitioners. Hillecke et al thus proposed a working factor model based on five ingredients or working factors that seem to be central aspects of music therapeutic work. The five factors are the attentiveness factor, the emotional factor, the cognitive factor, the motor behavioural factor, and the interpersonal factor. The authors suggest these five factors as a common theoretical basis for music therapy work. In addition, the literature mentions a sixth factor which might be of significant importance for future music therapy research and clinical use: the physiological factor. There is some evidence that music may induce physiological responses through the hypothalamic-pituitary axis. Another challenge in the field of music therapy is the specificity problem. It is difficult to tell whether an observed change is due to the music itself or to other contributory factors like the therapist-patient relationship. Many authors suggest that music can influence the neuronal plasticity of our brains in several favourable ways. With regard to music as treatment for pain, a meta-analysis revealed that the clinical significance of music is unsure. However, the possible physiological effects of music, an other possible indirect effects of music on pain processing should be investigated.