TellZall's object for April is the 45 rpm record.

In 1877 Thomas Alva Edison, who was born in Milan, Ohio, made the first recording of the human voice when he recited "Mary Had a Little Lamb" into his newly-invented phonograph. The following year, the inventor patented his discovery and began the process of developing it for market. The phonograph was an immediate commercial success.

Edison's phonograph used wax cylinders to record sound. In 1887 German immigrant Emile Berliner filed a patent for a phonograph system that used a flat disk in place of the cylinder. Berliner's "records" were easier to mass produce. The industry eventually standardized on a record that was ten inches in diameter and revolved at 78 revolutions per minute (rpm). The recordings played for about five minutes.

In 1948 the Columbia company introduced a new, twelve-inch record that played at 33 1/3 rpm, which gave twenty-three minutes of music and certainly made consumers of classical and opera music happy.

That same year, RCA Victor introduced a new record: the seven-inch, 45 rpm. The company also marketed a new record player that used the disks. At the same time, a new wave of music was rising as rhythm and blues evolved into rock and roll. The 45's shorter recording time suited the new music, and the two grew together in booming post-World War II society. Teenagers would rush to record stores to buy the latest hits from Chuck Berry, Elvis Presley, and others.

Just as the Beatles were climbing to the top of the record charts, in 1963 the Philips company introduced the compact audio cassette, which used magnetic tape. Cassettes soon caught on and, together with the compact disk that was introduced in 1982, forced an end to vinyl records, including the 45.

Additional Reading:
http://www.americanhistory.si.edu/notkid/r01.htm
http://www.45-rpm.org.uk/history.html