Paul McCartney has performed in stadiums and arenas all over the world. But what was he doing singing "I Saw Her Standing There" during a private graduation party at the Interlachen Country Club in Winter Park, Fla., with a local band on Saturday night?

As it turns out, it made perfect sense. The party's honoree was Arlen Shevell, the son of Nancy Shevell, who is McCartney's wife. While researching local bands on the internet for the evening's entertainment, Shevell came across Josh Walther and the Phase5.

“She called us about this event last year, but I didn't know who she was,” Walther told the Examiner. “I didn't figure it out until about two weeks ago when she casually mentioned it on the phone."

The day of the show, Walther could barely contain his enthusiasm in a post on his band's Facebook page. “Just a little nervous about our gig tonight. I am never one to be nervous before a show. However, tonight we are playing for one of my musical heroes and his family. Actually, I think it's safe to say that he might be the world's biggest living musical hero. Hopefully I can get through it without falling down or saying anything to embarrass myself or the rest of the band. LOL. Positive thoughts needed from all of my friends smile emoticon Can't say who until tomorrow. I'll just say ‪#‎MaybeImAmazed‬ I really am. Shocked, stoked, honored, terrified, but mostly AMAZED!”

Walther said McCartney began the evening on the dance floor, and during the band's break, he asked if he could sit in on a few songs. “He had us play a blues progression and he improvised a song about his stepson's graduation,” Walther continued. “And then we did 'I Saw Her Standing There.' We went through basically the whole catalog of Beatles songs we knew and he really wanted to do "[I] Saw Her Standing There," but we had never played it. Our piano player pulled up a chart off the internet and we just totally winged it. It turned out great.”

The bandleader said that McCartney "was really complimentary of the band" and was a “super nice guy and very unassuming. He seemed to want to hang out more with us, but his wife wouldn't have it. [He] told me I had the smoothest voice.” You can watch a video of the last verse of "I Saw Her Standing There," shot by one of the party's attendees, above.

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