They celebrate the most wonderful time of the year with seasonal confections that put the heart and soul into the holidays. With fresh arrangements, playful improvisation, and abundant good cheer, their big band arrangements of songs both sacred and secular feature the core group of grooving instrumentalists along with two charismatic vocalists: smooth-as-silk baritone Denzal Sinclaire and teenage phenomenon Alexis Morrast, a recent first-place winner of the nationally broadcast “Showtime at the Apollo.”