In an era of big music, big hair, big everything, the Waterboys were truly momentous. From 1983 to 1988, bandleader Mike Scott brought a wall-of-sound approach to electric folk balladry. If Lou Reed studied up on Celtic mysticism, and then tried to make a record that sounded like Van Morrison's Astral Weeks, the finished product might come close to replicating the Waterboys, whose early work forges a balance between being massive and graceful. Scott's lyrics often recall an ancient and verdant past, with the instrumentation emulating his favorite imagery. A serenade about early English paganism can become ritualistic and enchanting, and a love song will surge with the passion of an overflowing river meeting the sea. In the years since the original band dissolved, Scott has occasionally taken up the Waterboys mantle, and his most recent album contains lyrics composed entirely from the poetry of William Butler Yeats. But as a somewhat new Waterboys fan who is still obsessed with their first few albums, I find myself singing along to one song in particular: It begins, "I have heard the big music, and I'll never be the same." Neptune Theatre, 9 pm, $35.