In any Gamaka (Music), Alankara, or 'Inflexion', 'Ornamentation' etc., one can not have a 3rd type of note, other than a 'Shruti' and a 'Nada'. The threshold of identification of a musical note within the range of human voice of 100–1000 Hertz is 20–45 msec. Shrutis can be identified by the human ear because they are played for this time limit or more. As against this, connecting Nadas are played faster than this limit, which disallows the human ear to identify them. The major difference in the two systems is the way they combine shrutis and connect nadas, resulting in characteristically different music between the styles. Many ancient Sanskrit and Tamil works refer to 22 shrutis as the foundation of the Indian Music Scale.