According to Osho, chanting does not help one attain the aloneness of samadhi; it sustains the mind's addiction to duality by creating a 'you and the mantra' or 'you and God.' For true aloneness, drop all supports - no Ram, no Om, no images - stay utterly alone and let the mind's restlessness pass; without any 'other,' the mind dissolves and samadhi unfolds.
Chanting keeps you with an 'other'; for real samadhi, be silently alone and let the urge to chant or think fade.