Laertes wants to demur--he's not very good with a viol; he wouldn't want to take up Lan Wangji's time--but at the same time, he recognizes what a gift it is to be invited to share music. How closely such things touch Lan Wangji's heart (which, Laertes is beginning to suspect, is tenderer than he could have guessed). Just to confirm that he's read Lan Wangji's look correctly, he asks, "Wouldst have me play for thee?"