[1] It became so popular that the book was eventually "legitimized" by publisher Hal Leonard, and re-released in a series of editions and transpositions for various instruments.
For years, musicians had been producing "lead sheets", so called because they contained only rough outlines of music pieces rather than fully notated scores.
For this reason, the books were quickly adopted among jazz players in the 1970s, particularly on the East Coast of the United States.
These unlicensed books were all sold through informal connections, such as for cash in the backs of music stores, and between musicians.
In 2004, the Real Book material was acquired by the publisher Hal Leonard and licensed for legal sale.
[1] When Swallow was asked about the origin in February 2018, he said the book was written by students at Berklee who wanted to make money.
Swallow asked Bley and Steve Kuhn if they wanted some of their songs included, and they did; so they all contributed lead sheets.
One of them had a beautiful manuscript that subsequently became classic—it's called the Real Book font, and it imitates with uncanny accuracy his hand.
The April 1990 issue of Esquire featured The Real Book in the "Man at His Best" column by Mark Roman in an article called "Clef Notes".
The writer of the article, Michael Lydon, said, "I got mine in 1987 from a bassist who lives in Queens and who attended the Berklee School of Music in Boston; many in jazz circles suspect that students there reproduced the first copies of it in the mid-70s.
[1] In 2004, the music publisher Hal Leonard obtained the rights to most of the tunes contained in the original Real Book and published the first legal edition, calling it the Real Book Sixth Edition in tacit acknowledgment of the five previous illegal versions.