NASA announced the selection of seven test pilots, who became known as the Mercury Seven, for duty as astronauts on April 9, 1959. They were chosen to take part in Project Mercury, which was the first human spaceflight program (1959 - 1963) of the United States.
Ultimately, the goal was to put a human in orbit around the Earth. After 20 unmanned launches and two manned suborbital trips, John Glenn, Jr. piloted the Mercury-Atlas 6 flight on February 20, 1962, achieving this goal.
There were a total of four orbital flights with astronaut pilots. Donald Slayton was unfortunately grounded during the project due to irregular heartbeat, but was reinstated later, and flew on the Apollo-Soyuz Test Project in 1975. The other five who did fly during Project Mercury were Scott Carpenter, Wally Schirra, Jr., Gordon Cooper, Jr., Alan Shepard, Jr. and Gus Grissom.
The NASA project name of Mercury Seven lead me to choosing a track called "Seven Seas Of Rhye", written by Queen's Freddie Mercury, as the 'Today's Tune' selection. There was an instrumental version on 'Queen' (1973), the first album by the regal band. However, it's the more complete version from 'Queen II' (1974) that made the cut.
Queen - "Seven Seas Of Rhye" (1974)
Queen - "Seven Seas Of Rhye" Live (July 12, 1986)
From 'Queen Live At Wembley Stadium' DVD (2003)