On the one hand, Rav Moshe gave a heter for music during the year since we are a nervous society and music calms the nerves. Also, the dancing “macholos” referred to in halacha is skilled fancy step dancing, not putting one foot in front of the other that is done at many simchos.
On the other side, there are poskim who hold that the instrument player which produces sound from tapes, records, CDs is no different from any musical instrument that produces music sound.