Because all good things must pass - and the Roman alphabet only has 26 letters - the WXPN A to Z is about to come to a close.

The last couple of weeks - the alphabetical marathon began on Nov. 30 with the Jackson 5's "ABC" and will end 6000 or so songs with a tune that begins with the letter Z sometime on Saturday - have made for some highly entertaining left-of -the-dial listening at 88.5-FM.  

It's been a bravura programming performance and pretty brilliant promotional move that certainly gets the point across that the University of Pennsylvania public radio draws from a much larger music pool than your average tightly scripted commercial outlet. "A radio station that doesn't repeat a song - for weeks!," as deejay Eric Schuman put it in one promo insert, certainly gets the we-have-a-voluminous-library point across.

Sure, I have my nagging complaints. I didn't hear a single hip-hop song in any of the more than a dozen stretches I listened, and I had a hard time finding any while perusing the list at Though hey, Snoop Dogg's "Gin & Juice" was in there.

And the alphabetical order by song title 24/7 stream sometimes gave me cause to gripe: During a four song "sit" stretch I was pleasantly surprised by Buffalo Springfield's "Sit Down I Think I Love You" (didn't know that one) followed by Otis Redding's "Sittin' On the Dock Of The Bay" (awesome, of course) and Jimmy Cliff's "Sitting In Limbo" (also great). So next up had to be Howlin' Wolf doing "Sitting On Top Of The World," right? Nope. Sorry, it was Jack Johnson's "Sitting, Waiting, Wishing." Arrrggh!

But of course, that's been the fun of the A to Z, which makes you guess what'll come next and has kept me listening in the driveway on multiple occasions with don't-touch-that-dial piqued interest. They're in the W's as I write. "What" songs included the Beatles' "What Goes On" and the Velvet Underground song of the same, done by by VU and the Feelies. Plus Jimmy Ruffin's "What Becomes Of The Broken Hearted" (also covered by Joan Osborne), as well as Tower of Power's "What Is Hip," Black Uhuru and George Harrison's "What Is Life" (different songs) and a musical question asked by Morrissey: The Smith's "What Difference Does It Make?"

The answer is, quite a lot for people who are deeply into XPN.  The station is expert at creating a community of listeners who have been hashtagging #XPNAtoZ for weeks.  Their song of the month could have been a Faith No More banger that didn't make the cut: "We Care A Lot."

Particularly impressive in their devotion are the likes of superfan Drew Sudell, whose Twitter bio ID's him as "software developer, would be student of technology and innovation, nerd." His "Textual Analysis of XPN's AtoZ playlist" number crunching shows that, not surprisingly, more songs were played by The Beatles than any other artist, with over 120 as of Friday morning. The Rolling Stones, Bruce Springsteen, Bob Dylan, Neil Young, Led Zeppelin, Grateful Dead , David Bowie, R.E.M. and (egad!) Steely Dan round out the dude- and classic rock-heavy top ten.

Other Sudell findings: the most frequent first word was "The" (ranging from The Clash's "The Call Up" to Little Eva's  "The HaLoco-Motion" to Gordon Lightfoot's "The Wreck Of The Edmund Fitzgerald," followed by "I" and "Love," with most of the latter played by the station's drive-time leading man Dan Reed, including Donna Summer's "Love To Love You Baby."

More wonky analysis, with color coded graphics, comes from Lena Bartell, whose data mining shows The Ramones (with “Do You Remember Rock n Roll Radio?” and “Do You Wanna Dance?”) and Flying Burrito Brothers ("Hot Burrito #1" and "Hot Burrito #2") as among the artist who have scored alphabetically consecutive songs, and 1970 to be the most popular song year.

The kick of the A to Z has been wondering what’s coming next, and knowing that it won't be something you heard earlier in the day, or yesterday, or even last week. Or as Dave Matthews put it on Friday afternoon in another musical question that I did not particularly enjoy: “Where Are You Going?” Happily, the answer was to next listen to The Supremes’ “Where Did Our Love Go,” and soon thereafter to ponder another query, posed by Ray Davies and The Kinks, that A to Z enthusiasts will be askig themselves once the marathon is over: “Where Have All The Good Times Gone?”