Reedmace Star brought to our attention an invitation for folks to sing in a Brony Choir. NerdyAslin is the one putting out the call—you can hear all about it here. The first project they're tackling is The Heart Carol, and they're using Reedmace Star's arrangement.
Since NerdyAslin make a (joking) request for an arrangement of Pinkie Pie's Welcome Song, Reedmace Star made a (joking) response. Here it is, in four-part glory: Welcome Song sheet music. There's also a midi and a Lilypond version, and the video contains the very cute visualization.