A Solo is a part of a song where the instrument stands out in the song. Usually, a solo consists of a guitar but can also be a keyboard, drums or sometimes a bass solo.
When a solo starts, the highway turns blue, and a counter of percentage scored shows up over the highway. Completing a solo will give the player score depending on the percentage, with at least 60% or else it will be a "Messy Solo" which gives 0 points.