Introduction
The term Guitarsolo refers to a specific Nightbattle Setup on Destroyers. It has been coined by DuskofDawn in this thread
Setup
Outside of Tashkent, this requires you to have a Reinforcement Expansion on a 3-slot DD. Note that this setup only works on Destroyers.
The setup consists of a Small Main Calibre gun (preferrably D-Series) 
, A Surface RADAR 
, A Torpedo Launcher 
and a Skilled Lookout 
in the Reinforcement Expansion.
It derives its name from the Main ingredients: GUiTaRSolo, referencing the Gun, Torp, RADAR and Skilled Lookouts (SLO).
Merits
Guitarsolo allows the DD to get multiple rolls on Nightbattle CIs, improving the chances to roll one of them significantly. The CIs to be rolled are all single-hit attacks.