I recently attended Shabbat morning services at a synagogue that was having a "Carlebach Shabbat". A group of "Carlebachians" led the services, and sang many of the prayers to music composed by the late Rabbi Shlomo Carlebach.
I happened to be sitting next to one of the organizers of this Shabbat event, and I asked him: what does a "Carlebach Shabbat" service provide, that seems to be lacking in the "regular" synagogue service? He pondered for a few moments, and then answered in one word: "Yearning".
I have been pondering this response ever since.