“Busy” is a word that barely describes keyboardist Will Rast’s gigging schedule. Playing in no less than six ensembles, Rast has steadily become one of the more visible musicians in the area, spreading his tentacles throughout the District’s music scene. His work has garnered Wammie nominations, gigs at notable venues across the country, and international tours with pop star Mya. If that wasn’t enough, Rast and his fiancée are tying the knot next month. While…