How do I advise someone who listens to music in a way that doesn't make them alienate me?

Kindness is commendable in all matters. Advising someone who commits forbidden acts, such as listening to musical instruments, should be done with the best and most gentle approach to ensure the advice is accepted. Explain to him that you are advising him out of fear for him and love for him. Praise his good qualities to encourage him to abandon what Allah has forbidden. Mention to him the wisdom behind the Sharia (definition)'s prohibition of musical instruments and their effect on the heart. Explain that abandoning them might be difficult at first, but it becomes easier with striving, occupying oneself with what is beneficial, and devoting oneself to the Qur'an.