Bob, one thing I've experienced with essentially the same choral assignments per Mass time for 18 years is that my auditioned choir, our "schola", is comprised of individuals who are highly motivated, some choosing to do two Masses, others choosing to experience their Sunday "day of rest" with intent and purpose. Therefore, we've kept that earlier Mass, 8:30am, designated as the equivilent of a Solemn High (or at least Missa Cantata) Mass to accomodate their varied needs family and social wise. They also know that in addition to the pre-eminent Masses (Triduum, Midnight Christmas, etc.) that they are the go-to choir for other "high profile" Masses as they arrive at our doorstep. The later Mass, 10:30am (which was at 10am until a recent alteration due to our opening of the fourth parish in our merged cluster) has a stable "Y'all come sing" base, that can function quite successfully with minimal rehearsal and a fluctuating size/voice distribution. Quality will attract more quality. What's been really odd of late is that some folks come up after the later "ensemble" Mass interested in participating in that group who are actually better suited for the more demanding schola choir. So, once I've appraised them of that choice, they opt for more strenuous rehearsals on weeknights, and the earlier Mass on Sunday.

We don't assess "vitalization and growth" upon Mass attendance. Happily, since the fourth parish opened, the mother parish has not suffered any consistent drop; in fact, because the nature of the two principal morning Masses has remained constant, while the new parish is crafting and evolving into its own "character" (for lack of a more apt term) attendance sometimes spikes mightily into SRO.

We're very fortunate in our little town and mini-See in that regard.