I picked Bruce Springsteen (The Boss, and arguably my favorite musician for a while; I love his music, and, after taking that class on Romantic Poetry where the prof. played Bruce every few days, I still can't get his lyrics out of my head) and Ralph Vaughan Williams, one of the lights of British composing from the first half of the twentieth century. If you've sung in a choir (as I have), you've sung Vaughan Williams.

So here's how it goes: Bruce Springsteen was influenced by The Beatles, which contained bandmember Paul McCartney. McCartney wrote music that was performed by U2, who performed with Luciano Pavarotti on Miss Sarajevo (this isn't listed on allmusic, but I have the MP3 to prove it!). Pavarotti has performed with the London Philharmonic Orchestra, who've done works by Vaughan Williams.

Bruce-Beatles (Paul McCartney)-U2-Pavarotti-London Philharmonic-Vaughan Williams.

I think that counts as six, exactly, unless you want to press the distinction between McCartney and the Beatles. Although I'm also sure someone can do this pair quicker if they try.