Since 1992, the composer Phil Kline has hosted an annual event between Thanksgiving and Christmas that serves as a kind of semi-secular carolling, a hybrid of sound art and holiday festivities. His “Unsilent Night” is a four-track participatory composition. Individuals put one of the constituent parts, each 45 minutes in length, onto tape, CDR or an MP3 player, and broadcast them in unison in public, originally on boomboxes, now on all manner of equipment. The trick is that unison is hard to achieve, even if everyone assembled listens closely as the lead caroller counts down on a megaphone. The sounds are a mix of chimey percussion, resonant synths and some church-ready vocalizing. The four tracks are compressed into Zip files on Kline’s site and make for seasonal listening, before, during and after Xmas, philkline.com (ZIP, ZIP, ZIP, ZIP).