Compose a soothing and tranquil melody that incorporates the gentle sounds of nature, such as a babbling brook or soft rainfall. The composition should be slow-paced with a rhythm mimicking the pattern of a resting heartbeat. Incorporate soft, lulling instruments like the piano or violin, and consider using a repetitive melody to help induce a state of relaxation and sleepiness. The music should be long enough to assist in the full process of falling asleep, so aim for a length of at least 45 minutes to an hour.