Sleep is a basic behavior in humans. There are some research reports on the cyclical patterns of different types of sleep and their relationship to breathing, heart rate, brain waves, and other physical function. More recently, scientific research has begun to show how music therapy interacts with relaxation and sleep cycle. This research is focusing on the following hypotheses: 1. Music could influence physiological variables including blood pressure, heart rate, respiratory rate, EEG measurements, body temperature, as well as biochemical parameters within relaxation and sleep cycles. 2. Music therapy causes hormone secretion that results in relaxation. In this respect, melatonin is a hormone that contributes to the regulation of the human sleep cycle. Therefore, it is to be predicted that increased level of this hormone will cause relaxation. This descriptive cross-sectional study determined the relationship between music therapy, relaxation, and sleep cycle. Based on the obtained results, it can be suggested that light music promotes relaxation and regular sleep up to 75% of its value. This conclusion is especially supported by epidemiological studies.