Music is related to sound and sounds are of two types. First which that is used for music and second is, That which cannot be used for music. The sound which can be used for music is called Naad and the sound which cannot be used for music is called noise. In short we can say that a sound with a constant vibration is called as swar and this is the sound that comes in use of music, with sounds melodious to ears and gives joy to our soul. This sound in Hindustani classical music is called Naad.