Okay, the title is somewhat deceptive. Not many of these tunes are arranged in the barbershop style per se, but they're TTBB, and the melodies are generally in the second tenor part. The quartet is called "PowerMac", and they're synthesized voices created by software called VocalWriter, which is shareware that's only available for Macintoshes. (As of 8/2015, I'm running a Mac Mini with Snow Leopard just so I can use VocalWriter.) PowerMac consists of "Andy" on tenor, "Richard" on lead, "Robert" on baritone, and "Abe" on bass. Many of these MP3s are mono 24-bit sampled files to make them as small as possible.
I've assumed that all of these are in the public domain. I'm a little shaky on the availability of the Missouri songs, but I work at MU, and that probably accounts for something.
The Star-Spangled Banner Unusual among barbershop arrangements in that the second tenor has the melody except for the very last note or two.
Advance Australia Fair It was fun trying to make an American-developed program sing with an Australian accent.
Fratelli d'Italia Two national anthems stuck out in my hearing as being particularly cheerful: Italy's and Brazil's. The former sounds like a cross between a fight song and a drinking song, and the latter sounds like a march from a cartoon show.
Every True Son/Fight Tiger The fight song(s) of the University of Missouri - Columbia (Mizzou). The bridge between is usually chanted rather than sung.
Kimigayo The national anthem of Japan.
Old Missouri Mizzou's Alma Mater. Also the alma mater of a lot of other schools; the only thing unusual about this arrangement is the barbershop tag-style ending.
The National Anthem of Mexico in barbershop style; there are several chords in this that one has to have at least 3 semesters of music theory to name.
The Natioanl Anthem of Spain is one of the oldest established national anthems, and it has lacked lyrics until now. Yes, I wrote them, and they're silly, and I hope they don't cause an international incident.
Ave Maria The Bach/Gounod version. Abe, Robert and Andy sing the Bach keyboard part while Richard soars on the Gounod melody.
Psalm of Praise Based on a processional song from Cameroon, a country in western Africa.
Depth of Mercy Tune more or less by Sibelius, I think. How Great Thou Art An adaptation of the way the Statlers sing it. The English lyrics aren't old enough to be public domain.
Psalm 23 (The Lord is My Shepherd) Unusual in that each voice gets a different part in each of the four verses.
Lift Every Voice and Sing the official song of the NAACP.
Engelskanon Three Christmas carols about angels sung at the same time with a bass line added. I don't know what inspired me to name it in German.
He Was Born A happy little ditty in D. Wait, Robert, what are you doing on that second verse? Isn't that other song in e minor?
Joy to the World In 3/4 time. Once again, Robert sings something completely different on the third verse.
Linus' Monologue This is what Linus says at the climax of "A Charlie Brown Christmas". The music is by Handel, but it's sung as only PowerMac can.
Have Yourself a Merry Little Christmas Some very un-barbershop chord choices in there. Definitely not public domain.
The Grinch Song (You're a Mean One, Mister Grinch) Someone jumped through the hoops to get me the permission to do this arrangment, but I haven't seen the paperwork, so I'll assume I shouldn't put the MP3 up yet.
Welcome, Christmas The song the Whos in Whoville sing at the end of the cartoon version of "How the Grinch Stole Christmas". Not in the public domain yet.
The Hallelujah Chorus Edited a bit for length, and it's not easy covering both the orchestral and vocal parts, but somehow PowerMac gets it done.
Christmas Chopsticks (A Visit From Saint Nicholas) The tune should be familiar, as should the lyrics by Clement Clarke Moore.
The Secret of Christmas I just like this tune, and the arrangement turned out well, but it's not very barbershop-y. Too new to be in the public domain.
Christmas Opener (YouTube video!) Haven't heard this one? Music and lyrics by Hugh Emerson; tells the story of a group in need of a new song trying a new approach for song acquisition: ask Santa Claus for it!
Tacobell's Canon in D Yes, that one. As sung by a hungry barbershop quartet and an order-taker at a local Taco Bell.
Let's Do Something Cheap and Superficial The song struck me as funny. The arrangement is not one of my better efforts, so it's just as well that I can't post it yet.
Du Bist wie eine Blume PowerMac can sing in German, but their American accents are obvious. This is the first version, which is more or less as Schumann arranged it, but I've done a quartettier one since.
Evangeline A song by Will S. Hayes. Amazingly, the chorus is pretty much as he wrote it; he actually wrote the "Yes, she is gone!" line ably sung by Abe.
The Maple Leaf Rag With lyrics by Hugh Emerson, who shamelessly plugs himself therein.
Moonlight Serenade Glenn Miller's signature tune. Will have to wait a few years to put this one up.
Roll Over Beethoven I stuck a lot of public domain Beethoven cuts into a very non-public domain song.
Back in the USSR Based on the way the King's Singers sing it. Probably all sorts of copyright issues there.
Till there was You From the Music Man. Will be public domain someday.
Since You've Been Gone by Weird Al. Nice comedic arc. Obviously not public domain yet.
Just the Way You Are I really like the chords at the beginning of this one. Not public domain yet.
Naturally Doo-wop written for 5 parts, but in a quartet, you have to make do with 4. Duh. Not public domain, so it ain't here.