I remember Low Mass, High Mass, and Solemn High Mass. Low Mass was of course in Latin, one priest, only two candles, no incense, and no singing. High Mass was one priest, six candles, incense and holy water at High Funeral Masses, Sung Prayers and Responses. Solemn High Mass, Priest, Deacon, Sub-deacon (actually all three were usually priests but assumed the roles), incense, Sung prayers and responses, Hymns and Litanies. All had readings and a sermon, Last Gospel in Latin and prayers at the foot of the altar beginning and end, bells at the Sanctus and consecration. Not sure what the Pontifical Solemn Mass is. A Solemn High Mass in the Traditional Latin Format is something else again. You will think you have died and gone to heaven.