There's a pretty amazing Pipe Organ in the Sacred Heart Basilica and, following requests from some guitarists, I have inquired about the appropriateness of guitar music in the basilica. It is interested how it is approached by people who have been involved in the two different churches in the parish. Those at St Thomas' Church cannot see anything wrong with having guitars in the basilica; but those from the basilica are vehemently opposed! - in one case, citing writings from Various popes stating that the music must be appropriate for the building.
From Saint Pope John Paul II: Today, the meaning of the category ‘sacred music’ has been broadened to include repertoires that cannot be part of the celebration without violating the spirit and norms of the Liturgy itself. Not all the expressions of music are able to express adequately the mystery grasped in the fullness of the Church's faith. Consequently, not all forms of music can be considered suitable for liturgical celebrations. (Chirograph on Sacred Music, 2003)
Recently, I visited the Catholic Cathedral Parish in Palmerston North, which has a similar building. They have a guitar group, along with other instruments and play some quite "happy-clappy" music - and the congregation seem to enjoy it. (I was hoping for a glorious pipe organ and a choir, as the Musical Director has had plenty of experience in both). Maybe it was only because of school holidays - but the large organ in the gallery remained silent. Pity.
As it happens, there are two weeks at the beginning of July and at August where the 5pm Mass has lost its "organist" and I wonder whether some guitar music might be good for them?