The octave is the interval between a musical note and that of half or double its frequency. The octave is one of the natural elements of music, with two different notes producing the exact same pitch. In the Western tradition, while there are twelve chromatic, or precise half-interval, steps, the actual notation of each scale is on eight notes of differing spaces.

Gregorian chant is the style of music that developed throughout the Middle Ages, having various sources and styles. It was an ecclesiastical form of music, meaning that it was a "church" music. In particular, it was a kind of liturgical music, used in the various forms of public worship undertaken by the Latin Roman Catholic Church. Its melodies were based on the texts of the Mass, the Divine Office, and other liturgical ceremonies. Many of these texts were biblical, though adaptations from other sources are also found in many hymns and antiphons throughout the Middle Ages.

Strictly speaking, Gregorian Chant is a phenomenon of the Christian West. It was the liturgical music of the Latin Rite of the Roman Catholic Church, which dominated much (though not all) of Western Europe throughout the Middle Ages. While there were other forms of liturgical worship throughout this period, the Latin Rite was the "location" for the development of the Gregorian Chant repertoire. Its texts were taken from various parts of the liturgy, drawing on biblical sources as well as more original compositions by hymn and antiphon writers.

The pipes, trumpet, and harpsichord are not common Medieval instruments. Though is was an ancient stringed instrument also common in Medieval times, the lute was not associated with Apollo.

The Young Person's Guide to the Orchestra was conceived as a multi-media piece to educate children about orchestra music. Benjamin Britten's adaptation of the work of Henry Purcell, however, showed such great arrangements and inventiveness of instrumentation that it was immensely popular as an orchestral piece and record.

In musical notation, a clef indicates where the notes on the staff are placed, based on the clef symbol's position and shape. The three main clefs are, from highest to lowest in pitch, are the treble, alto, and bass clef. A neutral clef and an octave clef both indicate a non-traditional clef, with different emphases than the treble, alto, and bass.

Rock 'n' roll developed in the mid-twentieth century as a combination of other genres, such as blues, country, and jazz. Despite its eclectic origins, the music was usually stripped down, featuring limited combos. The typical instrumentation of a rock combo is one or more guitars, electric bass, drums, and occasionally a piano, organ, or horns.

A mandolin is tuned exactly like a violin, but with one key difference. Instead of having one string each tuned to G, D, A, and E, the mandolin has two courses of strings tuned in unison to each of these notes. The mandolin shares this trait with the entire "mando" family, including the mandola and the mandocello.

Jazz music developed around New Orleans in the late nineteenth and early twentieth centuries. Played by small ensembles featuring horns, pianos, and guitars, jazz was developed to have extended dances done with the music as accompaniment. As such, jazz began to promote its performers playing extended improvisations during parts of songs.

Although configured and played quite differently, both the accordion and the harmonica produce sound by having air blow over free reeds. While the accordion has buttons to open and close specific reeds, a harmonica player blows over a specific hole to create the desired tone.