Generally speaking, an album is any collection of audio recordings that is distributed as a single collection on compact disc (CD), vinyl, audio cassette (tape), or another media such as digital distribution. Originally, albums of recorded sound were individual 78-rpm recordings assembled in a bound book like a picture album; but, from 1948, this format evolved into single vinyl long-playing (LP) records played at 33+13/rpm, which are now the standard.
A time period known as the album era included the period from the mid-1960s to the early 21st century when the album was by far the most popular medium of recorded music expression and consumption. However, although vinyl LPs are still manufactured and distributed, record sales in the twenty-first century have been dominated by the CD and MP3 formats. During the 1970s and early 1980s, the 8-track tape was the first tape format to become widely used alongside vinyl records, and it was gradually supplanted by the compact cassette format. The cassette's popularity reached a peak during the late 1980s, then plummeted during the 1990s, and finally disappeared completely during the first decade of the twenty-first century.
There are album covers and liner notes that are utilised, and occasionally extra material is supplied, such as an analysis of the recording or lyrics or librettos for operas. A collection of numerous materials included inside a book format was formerly referred to as a "album." Beginning in the early nineteenth century in musical contexts, the term was used to refer to a collection of small pieces of printed music. Later on, groups of related 78-rpm recordings were packaged together in albums that looked similar to book-like binding (one side of a 78-rpm record could hold only about 3.5 minutes of sound). Upon the introduction of long-playing records, a collection of pieces or songs on a single record was referred to as a "album." As other recording media such as compact discs, MiniDiscs, Compact audio cassettes, 8-track tapes, and digital albums were introduced, the term "album" was expanded to include them as well.