Father Lee Kenyon explains that, "According to the old rules (Fortescue, et. al.) there are two types of standard Solemn Mass (i.e. non-pontifical, Requiem, etc.): Solemn High Mass (with deacon and subdeacon, smoke, etc.) and Sung Mass (also known as the Missa Cantata, with smoke, etc. but no deacon or subdeacon). The other form of Mass was the Low Mass. At Vatican II Rome abolished the distinction in the Novus Ordo so that there is just Mass and Solemn Mass."
(Photos of and by Fr Andrew Teather)