In Tantra sadhana, as the spiritual aspirant progresses in his/her realization, the spiritual development advances in 4 progressive stages depending on the sam'skaras of the aspirant. These 4 stages are also connected with the realization of 6 types of samdhi until the ultimate realization. These types of samadhi can be temporary or permanent realizations, same as the experience of higher samadhi depending on the sadhaka's samskaras. By the grace of the Guru, when the spiritual aspirant attains one-pointed concentration, first he may experience and/or hear a constant sound of crickets and feel a pleasant inner feeling of bliss. This is the stage when the kulakundalinii is in the Muladhar Cakra (Golden plexus). As the aspirant continues deeper in the repetition of his mantra, with one-pointed concentration, the kundalinii will rise upwards and pierce the second plexus, the SVADHIS'THANA CAKRA, and he/she will experience increased bliss and sometimes may hear the sound of ankle bells ringing incessantly. This first stage of samadhi is called 'SALOKYA'. The mental realization in this samadhai is: "I and My Lord are in the same level, same stratum" SALOKYA means: 'Same Loka or world'. With deeper and deeper meditation, the kundalinii will further ascend to the 3rd Cakra, MANIPURA CAKRA, as the serpentine force pierces this cakra, now the meditator will experience more intense bliss and he/she may hear the sound of flutes playing in unison. In this cakra the realization will be that "I am very close to my Lord" The experience of proximity with the Supreme is very intense here. This state of proximity is called 'SAMIPYA SAMADHI. Now, as the sadhana becomes still deeper, the sadhaka will experience greater bliss, very intoxicating bliss. This bliss is only experienced when the kundalinii shakti pierces the ANAHATA CAKRA, the Aerial Plexus. The sadhaka will hear the sound of sea waves or the sound of a gong, and will feel the tactual proximity with God. This tactual proximity with God is called in Tantra 'SAYUJYA SAMADHI' The bliss in this samadhi is indescribable. The Fourth Stage of Samadhi is called 'SARUPYA'. This stage is experienced when kundalinii ascends to the VISHUDDHA CAKRA, the Sidereal Plexus. Here in this level of realization the sadhaka will start hearing the Omnkara sound, and he/she will feel that "I and my Lord are One" Now the feeling is not only tactual but also of oneness. The bliss in this state is most intoxicating and usually a sadhaka may fall back unconscious. Now by the grace of God a sadhaka may attain the higher level of Sarupya Samadhi, that is, SARSTI SAMADHI. This samadhi is also called full SAVIKALPA SAMADHI. Here the aspirant will realize that "I am Brahma, I am He" The kundalinii here pierces the trikuti or the third eye and attains the stage of omniscience, the state of Luminous Vacuity. The bliss is beyond any description. Many sadhakas will hear the sound of Omnkara even after returning from this samadhi, and they will still hear the universal sound for days or weeks. And the final stage, the blessed stage of them all is when the sadhaka finally merges his own feeling of "I" in the divine ocean of objectless consciousness. Here there is no more "I' and "He'. It is either "I' or 'He" alone. This state is called KAEVALYA in Tantra or the state of NIRVIKALPA SAMADHI. The stage of Absolute Liberation. Shrii A'nandamu'rtijii describes this state as "This state of objectlessness being beyond the orbit of the mind, it is not mentally apprehensible. The lingering bliss that follows this state of vacuity is the proof of that state, the means of firm belief in that state."