As it was customary for rock bands since the 70's, there was usually a short acoustic set in the middle of most concerts, as a way to divide the show and give the audience the necessary transition from the excitement and emotion of the opening songs to the roller-coaster of the end of the gig, which usually included some of their best-known songs and some of the most powerful and energic as well.
The acoustic set was introduced in summer 1976 and at first consisted of only '39, but eventually other songs were added such as Dreamer's Ball (late '78 to early '79), Imagine (occasionally in late 1980), Life Is Real (sometimes in 1982) and, more famously, Love of My Life (first played in late 1977). For Crazy Little Thing Called Love, Brian began the song on acoustic, then switched to Telecaster and then ended it on the Red Special. Brian played Is This the World We Created (and the covers they did in 1986) on a guitar that looks and sounds like a classical acoustic but is actually electric (classical electric).
Brian's main acoustic guitars on stage have been:
1976: Martin D-18 six-string.
1977 - 1993: Ovation Pacemaker 1615 twelve-string.
1998: Collings six-string.
2005 onwards: Guild F-512 twelve-string.