In the nine angas of Bhakti as described in Srimad Bhagavatam, Sravanam comes very first. Thus, without hearing about Krishna, i.e. Hari Kathas on His names, forms, qualities, glories, pastimes, his devotees and associates, one cannot got to the next stage which is Kirtan. 

When one is well situated with such Hari Kathas, then the Kirtanam (chanting and singing) becomes very effective and real devotion sprouts in one's heart. Otherwise chantings, singings and nama sankirtans are not effective and becomes artificial and turns into another way of satisfying our material senses. 

So Sravanam is very important. 

Sravanam kirtanam vishnoh
Smaranam paada-sevanam
Arcanam vandanam daasyam
Sakhyam aatma-nivedanam     ..... (S.B. 7.5.23)

[The nine processes of bhakti are: Hearing,
chanting, remembering, serving His lotus feet,
worshiping, offering prayers, being a servant,
being dear, and offering one's atma itself to the Lord. ]