http://wapedia.mobi/en/Solemn_Mass
Solemn Mass (Latin: missa solemnis), sometimes also referred to as Solemn High Mass or simply High Mass, is, when used not merely as a description, the full ceremonial form of the Tridentine Mass, celebrated by a priest with a deacon and a subdeacon, [1] requiring most of the parts of the Mass to be sung, and the use of incense. The term “High Mass” is also used in the United States to describe the more common Missa Cantata, which lacks deacon and subdeacon and some of the ceremonies connected with them.
These terms distinguish the form in question from that of Low Mass and Missa Cantata.
The parts assigned to the deacon and subdeacon are often done by Priests in vestments proper to those roles.
A Solemn Mass celebrated by a bishop has its own particular ceremonies and is referred to as a Solemn Pontifical Mass.
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