“…The unmanifest Being [pure consciousness, Self] coming to direct experience establishes the reality of oneness of eternal existence: That is the pre-eminent path of gaining knowledge (of reality).
“There is no effort, no individual inception of the doer on the path to the experience of the unmanifest Being: Being can only be gained by making use of the thinking process without any reference to any existing thing, without meaning.
“With complete indifference (during meditation) to the thoughts relating to activities in the relative world, the direct experience of the Self is gained by one who turns away from all distractions.
“…Spontaneously moving in the direction of more and more [happiness] in the gap between impulses of Vedic sounds [mantra], there is the path to experience of the state of least excitation of consciousness for every human being born on this planet.
“…By means of the transformation of…the sound [to] greater abstraction and greater power, that impulse of Vedic sound becomes the cause of (the production of) soma…”
The sage Vasishtha, instructing Rama and the court.
Yoga Vasishtha Ch.5, v87-89, translated by Peter Freund, PhD
This is a reference to the approach I describe on Transcending. Other texts suggest you can transcend through any of the senses. However, because sound is the most subtle, it will take you deeper.
The science of mantra offers us sounds with known good effects that support purification and healing. Less suitable sounds can have secondary effects that are less desirable.
Then, using a sound with known good effects (Vedic sound or mantra) but without meaning, we avoid getting stuck in the mind on the way in.
The indifference mentioned is not indifference to life but indifference to the mind during the practice so we can settle beyond it. They also call this non-attachment or allowing. Indifference to life can arise from a resistance to what is. That is not allowing.
The increasing joy as we approach the bliss body and the peace of being draw us within when the senses are not busy with the outer world.
Even the mantra is transcended as we step into pure Being or samadhi.