Hearing and chanting about Krishna are the important foundations of spiritual life. Those who practice these two items of sadhana seriously will be able to cultivate the faith required to make spiritual advancement. The guru emphasizes hearing and chanting over everything else for this reason. Everything, including the understanding of chanting, is contained in the hearing process.
Lectures from a disciple Volume 1 "Spiritual Lives of Grhasthas", Pg 364-365