Surat is "attention" or "face", that is, an outward expression of the soul;[1] Shabd or Shabda has multiple meanings including ‘sacred song’, ‘word’, ‘voice’, ‘hymn’, ‘verse’, or ‘sound current, ‘audible life stream’, and the ‘essence of the Absolute Supreme Being’.
The Absolute Supreme Being is a dynamic force of creative energy sent out into the abyss of space at the dawn of the universe's manifestation, as sound vibrations.
Attaining this extent of self-realization is believed to result in jivan moksha/mukti, which is liberation/release from samsara and positivity in the cycle of karma and reincarnation.
Initiation by a contemporary living Satguru (Sat - true, Guru - teacher) is considered a prerequisite for successful sadhana (spiritual exercises).
Surat Shabd Yoga arose in India in the last several hundred years, specifically in the Sikh tradition (Nanakpanthi) founded by Guru Nanak.
Nada yoga is expounded in various Hindu scriptures such as the Nadabindu Upanishad, an ancient text affiliated with the several thousands-year-old Rig Veda.
However, a basic principle of Surat Shabd Yoga's tradition is the requirement for an outer Living Master to initiate followers onto the Path.
He wrote books "Moksha-Darshan (Philosophy of Salvation), "Satsang-Yoga", "Shri Gita-Yoga Prakash", "Raamcharit Maanas Saar-Satik", "Maharshi-Mehi-Padaawali" and "Maharshi-Mehi-Padawaali".
The Radha Soami movement of Surat Shabda Yoga was established by Shiv Dayal Singh (1818–1878) in 1861 and named "Radhasoami Satsang" circa 1866.
Soamiji Maharaj, as he was known, presided over the satsang meetings for seventeen years at Panni Gali and Soami Bagh in Agra, India, until he died on June 15, 1878.
More information on living masters related to Seth Shiv Dayal Singh Ji's lineage can be found in the Contemporary Sant Mat movements article.
This movement uses the Sound Current and ancient Sanskrit tones in order to traverse and return to the higher realms of Spirit and into God.
Altogether He teaches inner light (sight), inner music (hearing), primordial vibration (sense of touch), and nectar (taste and smell).
From Kabir to present, the Masters of the Divine Science of Light and Sound appear and manifest themselves as an uninterrupted line, through which they transmitted to each successor the one knowledge and the one Power.
Whereas in books when we read the history of Guru Nanak Dev Ji, we find no information regarding true merchandise of Word or Naam of God.
Among the exponents of Surat Shabd Yoga and the commonly shared elements related to the basic principles, notable variations also exist.