My fantasy is that Phish is familiar with the UK Manchester(aka "Madchester" Scene (1979-1992ish) and would play one of the great albums from that era. My choice would be The Stone Roses eponymous first album. A number of songs can be jammed (two were jammed on the album). Bonus Fantasy: Special guest stage dancer - Bez from the Happy Mondays (if he is permitted to travel).

Covering Joy Division's 'Unknown Pleasures" is probably a bridge too far, or rather, too dark. However, it would be fascinating to hear Mike's take on the bass parts.

If you aren't familiar with Madchester - I recommend checking out the relevant material on wikipedia. One link will lead to another. Also the movies: 24 Hour Party People and Joy Division (the latter is a documentatry, the former a docu-drama about the broader scene). Relevant Bands : Joy Division, New Order, Happy Mondays, The Stone Roses, The Fall, the Durutti Column and I would also include the Smiths.