We don't have synonyms for sing alongs yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are sing along, singalongs and sing-alongs.
(v) :
(idiomatic, music) To sing some music while someone else is singing or playing the same piece of music or while it is being broadcast or performed
(n) :
(colloquial, singing) A gathering or event where participants are encouraged to add their voices in song.
(v) :
(idiomatic, music) To sing some music while someone else is singing or playing the same piece of music or while it is being broadcast or performed
(n) :
(colloquial, singing) A gathering or event where participants are encouraged to add their voices in song.