Billy Martin

In late December 1969, Paul McCartney began recording new material using a Studer J37 4-track tape recorder that had recently been installed at his home in London. By January 1970, he began to consider that these recordings might form the basis of his first solo album. Wanting some secrecy for this project, he asked his wife Linda to book studio time at EMI Studios, Abbey Road, and at Morgan Studios under a pseudonym. Linda used the name “Billy Martin,” borrowing it from the American baseball player and manager.

You recorded your first album (McCartney) under the pseudonym BILLY MARTIN.

Well, sometimes if you don’t want people to know that you’re recording at a place – it’s quite widely done now – you use a fake name. For two reasons, really: fun and privacy. I think there’s a big character in American baseball called Billy Martin so that’s where the name came from.

Paul McCartney – Interview with Club Sandwich N°62, Spring 1992

From Wikipedia:

Alfred Manuel “Billy” Martin Jr. (May 16, 1928 – December 25, 1989) was an American Major League Baseball second baseman and manager who, in addition to leading other teams, was five times the manager of the New York Yankees. First known as a scrappy infielder who made considerable contributions to the championship Yankee teams of the 1950s, he then built a reputation as a manager who would initially make bad teams good, before ultimately being fired amid dysfunction. In each of his stints with the Yankees he managed them to winning records before being fired by team owner George Steinbrenner or resigning under fire, usually amid a well-publicized scandal such as Martin’s involvement in an alcohol-fueled fight.

Martin was born in a working-class section of Berkeley, California. His skill as a baseball player gave him a route out of his home town. Signed by the Pacific Coast League Oakland Oaks, Martin learned much from Casey Stengel, the man who would manage him both in Oakland and in New York, with whom he enjoyed a close relationship. Martin’s spectacular catch of a wind-blown Jackie Robinson popup late in Game Seven of the 1952 World Series saved that series for the Yankees, and he was the hitting star of the 1953 World Series, earning the Most Valuable Player award in the Yankee victory. He missed most of two seasons, 1954 and 1955, after being drafted into the Army, and his abilities never fully returned; the Yankees traded him after a brawl at the Copacabana club in New York during the 1957 season. Martin bitterly resented being traded, and did not speak to Stengel for years, a time during which Martin completed his playing career with various teams.

The last team for whom Martin played, the Minnesota Twins, gave him a job as a scout, and he spent most of the 1960s with them, becoming a coach in 1965. After a successful managerial debut with the Twins’ top minor league affiliate, the Denver Bears, Martin was made the Twins’ manager in 1969. He led the club to the American League West title, but was fired after the season. He then was hired by a declining Detroit Tigers franchise in 1971, and led that team to an American League East title in 1972 before being fired by the Tigers late in the 1973 season. He was quickly hired by the Texas Rangers, and he turned them for a season (1974) into a winning team, but was fired amid conflict with ownership in 1975. He was almost immediately hired by the Yankees. […]

Sessions booked under the name Billy Martin