there are more than enough examples of people using chanting to reach samadhi from pureland or vajrayana school. for example nianfo/Buddhanusmrti, it's known as 念佛三昧.
念佛三昧 The sam�dhi in which the individual whole-heartedly thinks of the appearance of the Buddha, or of the dharmak�ya, or repeats the Buddha's name. The one who enters into this sam�dhi, or merely repeats the name of Amit�bha, however evil his life may have been, will acquire the merits of Amit�bha and be received into Paradise, hence the term.
there are other form of samadhi 三昧 from different ways of "taming" the mind, hence the 84000 method. Buddha's idea is simply 戒定慧- discipline, concentration and wisdom. by stilling the mind with discipline, one is like stilling the water to see the bottom of the water/mind with clarity. there's a break through into insight/wisdom that might not be easy.
so any form of concentration can be refer as the simile of putting a stone on the grass so it stops sprouting, 石压�. not necessary chanting. when the concentration is gone, the grass grow back. we also have the boiling water as simile, when u are doing nianfo, the water is boiling, when u stop, the water start to cool down. as there's no constancy, awareness and mindfulness.
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�怕念起，但�觉迟 mean we are not afraid of wandering thoughts, but we need to aware of it before it's too late.
it's of no use if one chant with a wandering mind. then u might as well use other method of taming/disciplining the mind. our old master use reading and teaching dharma to tame his mind. teaching others is also teaching himself in practice. it's not easy to go wrong, when u have the Buddha's and ancient masters word as guide.
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