Musical languages are constructed languages based on musical sounds, which tend to incorporate articulation. Unlike tonal languages, focused on stress, and whistled languages, focused on pitch bends, musical languages distinguish pitches or rhythms. Whistled languages are dependent on an underlying spoken languages and are used in various cultures as a means for communication over distance, or as secret codes. The mystical concept of a language of the birds tries to connect the two categories, since some authors of musical a priori languages have speculated about a mystical or primeval origin of the whistled languages.