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The M'''issa Missa De Angelis''', or '''Missa VIII''', is perhaps the best known even among the assemblies that do not often have to do with Gregorian Chant. It normally bears the indication '''In festis duplicibus''' (Latin: ''Double Feasts''), and is generally performed on Solemnities.
Like all the Masses collected in the ''Kyriale Romanum'', it is a Mass whose pieces were assembled after years of being composed and sung. The centuries of composition of the five cantos of the ''Ordo Missae'' (which are the ''Kyrie'', the ''Gloria'', the ''Sanctus-Benedictus'' and the ''Agnus Dei'', the ''Credo'' was inserted later) are indicated in the same ''Kyriale'': the ''Kyrie'' is from the 15th-16th sec. (V mode); the ''Gloria'' of the XVI (fifth mode); The ''Sanctus'' of the 11th or 12th century. (VI mode); the ''Agnus Dei'' of the XV (VI mode). The ''Credo'' normally included in the ''Missa De Angelis'' is the '''Credo III''' (V mode), and is actually from the 17th century.<ref>''Kalos concentus'', sito di cultura medioevale; http://www.kalosconcentus.org/index.php/it/gregoriano/missa-de-angelis, url consultato il 26/07/2019</ref>