Handel's compositions include forty two operas, twenty nine oratorios, more as 120 cantatas, trios and duets (together about 2.000 arias), chamber music, a large number of ecumenical pieces, odes and serenatas and sixteen organ concerti. His most famous work, the oratorio Messiah with its Hallelujah chorus, is among the most popular works in choral music and today a centerpiece of the Christmas season. Also popular are "The Cuckoo and the Nightingale", in which birds are heard calling during passages played in different keys representing the vocal ranges of two birds; the Opus 3 and 6 Concerti Grossi.