Depending on your personality, composing a melody or a piece of music can either be extremely frustrating or a relaxing way to pass the time. If you find you fit into the latter category then ReBirth for the iPhone or iPod Touch might be just the app for you. ReBirth gives you a virtual synthesizer to work with to create your own music from wherever you are. It’s fully loaded and will take some experimentation to figure out all the options but for $6.99 it's a budding rock star's dream.