This continues from the post on the Collects. You won't understand it on its own.
The mass for Pentecost 1 is almost the same as that for Trinity 1, since BCP/S pushed these masses a Sunday later than T. The one difference is that BCP/S has (instead of the T Gospel) Luke 16:19 as the Gospel; a Gospel which does not appear in the T post Pentecosten masses.
The mass for Pentecost 2 is the same as that for Trinity 2. In other words, since Trinity 2 is a Sunday later than Pentecost 2, BCP/S is using this mass one Sunday later than T is using it.
Pentecost 3 mass is the same as that of Trinity 3; in other words, BCP/S is again using this mass a Sunday later than T is using it. EXCEPT that, as explained in the last post, BCP/S retains today an ancient Roman collect which T somehow has mislaid; while T precipitately uses the next collect in the list, which BCP/S correctly defers until next Sunday. So on this Sunday (and hereafter) the collects in BCP/S will be two Sundays later than in T.
Pentecost 4 mass is the same as that of Trinity 4; in other words, BCP/S once more uses the mass one Sunday later than T uses it. EXCEPT that (a) as far as the collects are concerned, BCP/S is running two Sundays later than T; today it uses the T collect for Pentecost 3; and (b) BCP/S here uses the Gospel which T gave us on Pentecost 1 (Luke 6:36). The T Gospel for Pentecost 4 is therefore displaced onto next Sunday, Trinity 5.
After this, things settle down. Thus most of the mass on Pentecost 5 is the same as that of Trinity 5 (i.e. T is using it a Sunday earlier than BCP/S, since the Fifth Sunday after Pentecost is a Sunday earlier than the Fifth Sunday after Trinity); except that the collects and Gospels have T now running two Sundays earlier than BCP/S.
I have been talking about BCP/S; i.e. the Sarum Mass, the Collect, Epistle, and Gospel of which are reproduced in the Prayer Book while the psalmody is to be found in the English Gradual and the back of the English Hymnal and the Secrets and Postcommunions are in the English Missal. In a couple of cases the 1662 Book slightly rearranged the clauses of Cranmer's collects; from time to time Cranmer himself slightly lengthened or slightly shortened an Epistle or a Gospel; and there are one or two little problems in some graduals.