I was fortunate enough a few years ago to see Brian with his solo band, which included Al Jardine and Blondie Chaplin (who sang "Sail On Sailor", my favorite Beach Boys song), with The Zombies (4 out or 5 original members!) there as co-headliners. Brian's encore was the following song, with him seated at the piano and the band gathered around him:
https://www.youtube.com/watch?v=m5CQygN_VCk