sing-along or sing·a·long [sing-uh-lawng, -long] WORD ORIGIN noun an informal or unrehearsed singing of songs by a group of people, usually under the direction of a leader; songfest. an occasion marked by such singing.
Origin of sing-along First recorded in 1955–60; noun use of verb phrase sing along Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019 British Dictionary definitions for sing along sing along verb (intr, adverb) to join in singing with a performer noun sing-along such a singsong Collins English Dictionary – Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012 Word Origin and History for sing along sing-along
1959, noun and adjective, from verbal phrase; see(v.) + (adv.). Originally associated with U.S. music producer Mitch Miller (1911-2010).
Online Etymology Dictionary, © 2010 Douglas Harper