Gov’t Mule is current in the midst of a European tour. During a rare day off, Warren Haynes stopped by to see Deep Purple perform at Amsterdam’s Heineken Music Hall. As first reported by the blog Here Comes the Flood, he also sat in with Deep Purple for “Black Night” during the group’s encore. Deep Purple bassist Roger Glover appears on the Gov’t Mule albums The Deep End and The Deepest End. Gov’t Mule previewed the collaboration earlier in the week by teasing “Smoke on the Water” during “Sco-Mule” at the Sala Heineken in Madrid, Spain. Earlier in the week Gov’t Mule also brought tour longtime friends Hook Herrera (harmonica) and Eric McFadden (guitar) for a series of songs at the Sala Apolo in Barcelona, Spain.