happening, natural event, occurrence - an event that happens

associate - any event that usually accompanies or is closely connected with another; "first was the lightning and then its thunderous associate"

background - relatively unimportant or inconspicuous accompanying situation; "when the rain came he could hear the sound of thunder in the background"

part, voice - the melody carried by a particular voice or instrument in polyphonic music; "he tried to sing the tenor part"

descant, discant - a decorative musical accompaniment (often improvised) added above a basic melody

vamp - an improvised musical accompaniment

protection - the activity of protecting someone or something; "the witnesses demanded police protection"

convoy - the act of escorting while in transit