Chicago and "25 or 6 to 4"

A collage used to promote Chicago in concert at the Chumash Casino Resort in Santa Ynez, California, 2005, Source

Chicago is an American rock band formed in Chicago, Illinois, in 1967. The group was initially billed as The Big Thing. They are a self-described "rock and roll band with horns" but also used elements of classical music, jazz, R&B, and pop music. They produced numerous top-40 hits over two decades and continue to record and perform live.

The band logo which appears in many styles
 on their album covers, Public Domain, Link

There had been a Chicago-based rock cover band with six members called the Big Thing that played in Chicago nightclubs and covered Top 40 hits. When the group began working on original songs in 1968, their manager, James William Guercio, wanted a name change. They became the Chicago Transit Authority but changed it after their first album to the shortened Chicago to avoid legal action being threatened by the actual mass-transit company of the same name.

Their first record (April 1969), Chicago Transit Authority, is a double album, which is rare for a band's first release. It made it to No. 17 on the Billboard album chart and sold over one million copies by 1970, and was awarded a platinum disc. The album included a number of FM radio hits – "Does Anybody Really Know What Time It Is?", "Beginnings", "Questions 67 and 68", and "I'm a Man." The band was nominated for a Grammy Award for 1969 Best New Artist of the Year.

Amazon lists an incredible 186 albums under their name, which includes studio albums, live recordings and many compilations in different formats.

Chicago II

One song on their second album is "25 or 6 to 4." It was written by Robert Lamm, a founding member of the band. The song title has confused many listeners.

In a 2013 interview, keyboardist Robert Lamm said he composed it on a twelve-string guitar missing the two low E strings. He said the song is about trying to write a song in the middle of the night. The song's title is the time at which the song is set: 25 or 26 minutes before 4 AM. But other interpretations emerged. One was that it meant a quantity of illicit drugs. Another was that it was the name of a famous person in code.