every parish should have under its belt a setting of the ordinary that it can sing without need of assistance from musicians.
No, no, no.
Please say, "sing without need of assistance from instrumentalists." Or "without need of musical leadership," if that's what is meant.
Those who sing, be they choirs, pew-sitters, priests, cantors. whatever - those who sing are musicians.
They are making music.
Priests, even tone-deaf ones must understand that they are obliged to produce music, they must be taught to understand that their singing THEIR parts, (dialogues, EP, etc.) recto tono if need be, is the sine qua non of a well-celebrated Mass With Music.