Tanz Zwo Drei Vier

Just downloaded Faderhead's "Tanz Zwo Drei Vier." This is the second song I'm familiar with that uses the word "zwo" instead of "zwei," so I did a little research and learned that zwo isn't necessarily regional, but used when you're naming other numbers. Examples: "Ich habe heute zwei Buecher gekauft" versus "Meine Nummer ist fuenf fuenf fuenf, null zwo sieben vier." Zwo is a more archaic form of zwei, feminine to zwei's neuter, and "zween" is the masculine form. No idea when if ever zween is used.