Similarly, Brahma sutras – the foundational text of the Vedanta school of Hinduism, discusses yoga in its sutra , and others.  Brahma sutras are estimated to have been complete in the surviving form sometime between 450 BCE to 200 CE,   and its sutras assert that yoga is a means to gain "subtlety of body" and other powers.  The Nyaya sutras – the foundational text of the Nyaya school, variously estimated to have been composed between the 6th-century BCE and 2nd-century CE,   discusses yoga in sutras –50. This ancient text of the Nyaya school includes a discussion of yogic ethics, dhyana (meditation), samadhi , and among other things remarks that debate and philosophy is a form of yoga.   
According to the Hamsa (swan) Upanishad, nada manifests itself as ten different sounds, which are heard by adepts and yogis in the subtle planes in the progressive stages of their spiritual advancement. Hearing them is a sure sign of success on the path. These sounds are the sound of cini, of cini-cini, of bell, of conch, of harp, of cymbals, of flute, of kettle drum, of tabor and of thunder clap. Of these only the last one should be cultivated. Different physical symptoms said to arise in the mind and the body as these sounds are heard, such as shaking of the head and sweetness in the mouth. When finally the last mentioned sound (thunder clap) is heard, one becomes identical with the transcendental Self (para Brāhman). The tantra shastras recognize Aum as the seed (bija) mantra and suggest its association with other mantras and names of Siva, Shakti and other divinities so as to increase their potency and vibration and hasten the process of purification and self-realization. Some of the well known and powerful mantras which are used in association with Aum as the prefix are mentioned below.