WordNet sense 1 (containing or using responses or antiphons recited or sung in alternation):

antiphonal

WordNet sense 2 (readily reacting to suggestions and influences):

amenable, tractable

WordNet sense 3 ((often followed by `of' or `to') yielding readily to or capable of):

susceptible

WordNet sense 4 (being susceptible to the attitudes, feelings, or circumstances of others):

sensitive

WordNet sense 5 (replying):

respondent