Over their 27 years, Phish has made sport of injecting others’ songbooks with their patented jammery, spiking sets with songs by everyone from Talking Heads and Zappa to Ween and the Stones. On Halloweens they do a whole album (The White Album, Dark Side, Quadrophenia, etc. and etc.). This tour they’re unveiling a new cover at each show, and lately they’ve begun aiming for bits that make hipsters tick: not so long ago it was TV On The Radio, on Saturday they upped the ante with their first stab at Neutral Milk Hotel, at the venue called Merriweather Post Pavilion. Double whammo. If you’ve always felt “Aeroplane” needed more guitar solo, this is your lucky day. Otherwise you should probably pretend this didn’t happen.