Q: 1) Regarding a parish church’s titular solemnity: How widely is this celebrated in the parish? – By a priest assigned to the parish, praying his Office elsewhere? At Mass in the chapel of a convent attached to the parish? By lay members of the parish praying the Office at their homes?
2) The above question, but for the anniversary of the parish church’s dedication.
(I ask separately in case they have different answers. It would seem at least possible that celebrating the anniversary of dedication is proper to that building, while the celebration of the titular feast would be more broadly proper to the parish community.)
A: There’s no clear answer to this from the liturgical books, but I interpret the norms on the calendar and the table of liturgical days this way:
I believe that both questions result in similar answers because they have to do with the building more than the parish. The celebration of Mass is a solemnity in both cases inside the building, but not in nearby chapels dedicated to other patrons.
The Liturgy of the Hours, which is often prayed in the rectory or in homes would fittingly be that of the solemnity because the same people would be gathering at the church if that were the location for the office.
However, if one or more persons prays the Liturgy of the Hours inside a nearby chapel dedicated to a different patron, it would not apply. If a priest assigned to the parish is out of town, I believe it would not apply to him.
Chapels are not formally dedicated as are churches. They are blessed. We don’t have clear guidance about the status of the titular day and blessing anniversary for those locations. Because they are chapels and not churches, such days are probably better observed as feasts than as solemnities.
But you can probably find people to disagree with me.