Albums of recorded music were developed in the early 20th century, first as books of individual
78rpm records, then from 1948 as vinyl
LP records played at
rpm. Vinyl LPs are still issued, though in the 21st century albums sales have mostly focused on
compact disc (CD) and
MP3 formats. The
audio cassette was a format used in the late 1970s through to the 1990s alongside vinyl.