Falsetto     
Falsetto is the maximal elongation of vocal cords with minimal glottic gap. It can be produced at almost any frequency, but is mostly produced in the upper range for both male and female voices. Falsetto was originally called "false voice" because of the use of castrates (castrated males) when women were not allowed to sing in churches.

It is the breathy sound that occurs when the vocal cords are allowed to separate. Falsetto will not blend with chest voice, therefore making it impractical to use except for special vocal stylings.