They're accompanied with abundant amounts of online information--text, images, video, and interactive pages. Here's one that lets you be your own Charles Ives. It combines Taps, played by a single trumpeter, with a marching band. The trumpeter stands in a skiff on a New England pond; with your mouse, you can place him off in the distance, or bring him in to shore, as the band plays on (or not). Charles Ives had a fondness for this kind of aural scene-setting--give it a try for yourself.