Elvis Presley, seated, jams with Jerry Lee Lewis, left, Carl Perkins and Johnny Cash at Sun Studio in Memphis, Tennessee. -- Photos from Sun Media files

It was a memorable moment in the history of Sun Studio. One day Jerry Lee Lewis and Carl Perkins were busy rehearsing when Elvis Presley dropped in unexpectedly, followed a short time later by Johnny Cash who came to collect his royalty cheque.

Many musicians recorded at the legendary studio over the years, but rarely had some of the best all assembled in one room at the same time.

Studio owner Sam Phillips knew the moment shouldn't pass unnoticed and called the local newspaper. The next day, a photograph of the musicians appeared on the front page along with a story about the "Million Dollar Quartet" jam session.

'ROCK AND ROLL HISTORY'

"It's one of the most famous photos in rock and roll history," explains tour guide Amy LaVere, standing next to a poster-sized copy of the image that hangs in the studio today.

Phillips recorded that jam session, but there was one problem. Elvis was under contract with RCA Records at the time, and Phillips feared legal troubles for making an unauthorized recording. So he kept the existence of the tape a secret, even after Elvis died.

It wasn't until recently that the rare audio recording was released completely unedited for the first time. Today, visitors on a tour of the studio can hear a portion of that recording, in which the four music legends sing songs, tell stories and even hit a few sour notes.

Sun Studio may be most famous for discovering Elvis Presley (who made five records here), but it was also known for giving many local artists, both black and white, their start in the recording industry. These included Roy Orbison, B.B. King, Charlie Rich, Rufus Thomas, Conway Twitty and Billy Swan.

In 1951, Jackie Brenston and the Delta Cats -- with Ike Turner on piano -- recorded Rocket 88 at Sun Studio. The success of the tune, which most music historians consider to be the first rock and roll song, led Phillips to start his own record label.

Another early rock and roll hit for Sun was Carl Perkins' Blue Suede Shoes. Jerry Lee Lewis had the two biggest hit records -- Whole Lotta Shakin' (recorded in one take) and Great Balls Of Fire, while Johnny Cash became the studio's most consistent hit-maker.

According to our guide, Phillips did not consider Elvis to be his greatest discovery, but rather a man named Chester Burnett, better known as Howlin' Wolf. Phillips reportedly said when he heard Howlin' Wolf sing, you could see clear into the man's soul.

Sun Studio opened its doors in 1950 and closed 10 years later when Phillips decided to search for larger quarters. The studio remained vacant for most of the next 25 years. In 1985 Carl Perkins, Roy Orbison, Johnny Cash and Jerry Lee Lewis returned to the empty studio to record the Class of '55 album. Shortly after, a music fan re-opened the site as a tourist attraction and working recording studio with Phillips' help. It's now a National Historic Landmark.

Structurally, everything including the floor is original. Phillips had designed the room after reading an article in a popular science magazine about acoustics. He built the control room and installed a wavy ceiling to prevent echoes.

Unlike many museums that prohibit touching or even photographing objects, here you're free to play a few bars on the piano once used by Jerry Lee Lewis or take a photo of yourself with the same microphone used by Roy Orbison and nearly every other famous musician who sang here.

The Sun Studio building is a U.S. National Historic Landmark.

On the floor, an "X" marks the spot where Elvis stood when he recorded his first hit song.

"When Bob Dylan visited the studio, he kissed the floor where Elvis stood, so you can kiss Elvis' feet and Bob Dylan's lips vicariously through that "X," offers LaVere.

For more on Sun Studio tours, see sunstudio.com.

PRISON BLUES

In 1953 Sam Phillips faced a hefty legal bill and was in danger of losing his studio. He needed a clever gimmick or something that would sell quickly, and found it in a group of five criminals from the Tennessee State Penitentiary who had formed a vocal group. He arranged to have them come into the studio to make a record.

The Prisonaires arrived with their feet in chains, shackled together and surrounded by armed guards. The song they recorded, Just Walkin' In The Rain, which you hear on the tour, was a hit. The recording helped Phillips financially. It also worked out well for The Prisonaires. The governor of Tennessee was so pleased, he gave them all complete pardons.