Interesting--for the post-V II liturgy, there is no common of Apostles in the Missal, but there is in the Gradual and Office. The Missal notes "For each Solemnity and Feast a complete proper Mass is provided." Each Apostle has a Feast, ergo no need for a common in the Missal.
In the Gradual, many of the specific chants listed for the Apostles' feasts are in the common, but some are specific to one feast only and a few come from elsewhere in the year (for example, the Communion for St Thomas's feast is taken from the Sunday after Easter, when the Gospel of Doubting Thomas is read). So it appears that the Common of Apostles in the Gradual is a repository for chants that are used for more than one Apostle. An exception seems to be St John (Dec 27), whose Mass uses two chants from the Common of Doctors of the Church.
In the Office, however, there are some chants--the invitatory antiphon comes to mind--that are used for multiple Apostles' feasts, so there may be more of a need for a common office of Apostles.
In the EF there is a Commune Apostolorum for the Office, but the Masses are all proper (although one quickly observes chants that are used by multiple Apostles, such as the Mihi autem introit).
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