Eight instruments playing together wouldn’t raise an eyebrow in the world of chamber music, but what if all eight of those instruments were cellos? That would be unusual indeed. But Harvard residents will be treated to just such a concert by the cellist octet BoCoCelli. The musicians are all students at Boston Conservatory at Berklee, and the one-hour program will include everything from choral music to Brazilian dance music, as well as premieres of pieces by two Navajo composers.