CBS Laboratories worked with a team at Columbia Records to develop a
phonograph record that would hold at least 20 minutes of music per side. The
research began in 1941, was suspended during World War II, and then resumed
in 1945 Columbia Records unveiled the LP at a press conference in the Waldorf
Astoria on June 19, 1948 in two formats: 10 inch in diameter, matching that of 78
rpm singles, and 12 inch in diameter. The first catalogue number for a ten-inch LP,
CL 6001, was a reissue of the Frank Sinatra 78 rpm album set The Voice of Frank Sinatra; the first catalogue number for a twelve-inch LP, ML 4001 (above), was
the Mendelssohn Concerto in E Minor for Violin and Orchestra, Op. 64, played
by Nathan Milstein with the Philharmonic-Symphony Orchestra of New York
conducted by Bruno Walter. These two albums are considered to be the
first long-players.