In the 21st century, it is often said by those selling singing techniques, books and methods that most people can learn how to sing. In fact, scientists have stated that the human larynx is typically very similar across all humans with only a difference in sizes. It is however a commonly held belief that singing is reserved for only a few which are born with the ability. Because of the difference in vocal fold sizes, some people are less capable of hitting higher and lower notes in chest voice (tenor can't hit much below low c, most untrained baritones can't go much above middle C). Knowing one's tessitura is important, the song must be in a key suitable for you, otherwise you are likely to look quite the fool as you break and go into falsetto or head voice in inappropriate places. The human larynx is an instrument, in which all that is necessary in order to sing is to learn how to use it, and practice often. With a little bit of motivation and patience, it can be achieved.