Nada Yoga (union through sound) is an ancient metaphysical system from India. It is a philosophical system and, as the name suggests, a form of yoga. Theoretical and practical aspects of the system are based on the premise that the entire cosmos and all that exists in the cosmos, including humans, are composed of sound vibrations called nada. This concept states that the universe is sound energy in motion, rather than matter.

The system of Nada Yoga divides the music into two categories: internal music (anahata) and external music (ahata).

External music is transmitted to the consciousness through the ear where mechanical energy is converted to electrochemical energy in the brain and then transformed into the sensation of sound. This is ahata, which is considered responsible for the receipt of the external music.

The student hears internal music through listening the inner sounds of the body. This process of inner awareness leads to increased sensitivity, self-reflection and, finally, awakening. The focus on inner sound as a support for meditation is very helpful to master the mind. Since it is tangible, this practice can penetrate all matter, a practice of vibration to be eternally in all Creation (samadhi).

In the West, detailed guidance and advice is given by Edward Michael Salim in his book The Law of Attention on Nada Yoga and the way to achieve self control. Ajahn Sumedho, of the Thai tradition, also teaches the practice of inner sound.

Nada Yoga is also a way to approach the sounds with reverence. Sound and music, in this context, are more than just a sensation that gives sensual pleasure. The sound and music act as a potential means to achieve a deeper union with both the outside and with the inner cosmos.

Music has been used by researchers of India, and by the prophets, as an important and powerful tool for the attainment of nirvana. Important persons in the study of sounds include: Thyagaraja, Kabir, Meerabai, Namdeo, Tukaram and Purandara Dasa.