I've just spoken on the phone with a friend from Lancaster, PA, Philip Crnkovich. He runs a schola known as the Te Deum Laudamus Singers, and they're looking for new members. Men who are interested (It's an all-male schola), please contact me at hocket [at] gmail [dot] com, and I'll pass along your information to Philip. This is a worthwhile venture. If you are a good singer who is familiar with Gregorian chant, please consider joining them; their membership is dwindling through no fault of their own and they need your help.
When I lived in Lancaster, the Te Deum guys were my lifeboat. It was the one chance each week I had to sing exclusively traditional music. We also like to eat lots of pie and ice cream together while discussing anything from the latest Vatican gossip to the ionosphere. (Well, okay, it's really only one person that likes to talk about the ionosphere, but it makes for good fun.)
The Te Deum Singers travel from place to place as needed to provide music for the Holy Sacrifice of the Mass. They are not associated with any parish--which is the smart way to do this sort of thing. They have sung throughout the Diocese of Harrisburg, including at the Traditional Latin Mass celebrated at St. Lawrence in Harrisburg, as well as at the Basilica of the National Shrine of the Assumption of the BVM, where His Eminence Cardinal Keeler was once spotted in the choir loft stairway listening to them.
The singers are always looking for places where they'd be welcome to sing, and if you are a pastor or some other person of real authority (e.g. a music director) in such a place, please contact me as well at the address provided above.