The impromptu surprise appearances by Paul McCartney are starting to pile up (and well, at what point are they less of a surprise?). Performed at New York’s Grand Central Station (Friday 9/7/18) on the occasion of the release of his new album “Egypt Station,” reports had the show not exactly public, held behind blackout curtains for invited guests. So, the rest of us would have only heard McCartney on our way to Yonkers unless we dialed it up live on YouTube. No matter, this is a worthwhile performance for a couple of reasons — with McCartney still graciously game even with some of the old notes now out of his range, and he dusts off “I’ve Got a Feeling” an old fave from the “Let It Be” rooftop concert in 1969 — which isn’t well-known but obviously distinguishes you as a qualified Beatles fan if you know it. —Eric Gould