The Guest2's link: on that page is "SonneLematine" --

SonneLematine allows you to sing, play, or whistle canons with yourself (the popular genre commonly called round, such as "Three Blind Mice"). That is to say, you produce the music only once as the first voice, while the other voices will sound from your headphones or speakers, seemingly from various directions. What you hear is actually what you generated yourself only seconds before!

The result, a full-voiced round all of your making, can be replayed with an arbitrary number of repetitions. If you are satisfied, you can save it as an audio file. Such files can be played, burnt onto Audio CDs, reprocessed (reverb ...), and compressed, using common standard software tools.

So you can sing rounds without leaving your closet... *snf* ...it seems so sad.

~ Becky in Tucson