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.

While the term Neoclassicism typically refers to the Enlightenment trends that focused on ancient Greece and Rome, in music the term refers to twentieth-century music that looked back to the "Classical" music of the eighteenth century. The composers Igor Stravinsky and Alfredo Casella were important figures in this movement.

In musical notation, the note "piano" above a clef indicates that the music should be played softly. Often such a mark, sometimes abbreviated with just a "p," will come in the middle of a piece to indicate a change of volume. The opposite notation is "forte," which indicates that the music should be played loudly.

Philip Glass was part of a group of composers who used simple motifs that were repeated over steady beats. This music was dubbed "minimalism" by crtics, but also embraced by the figures who founded it, as it expressed their desire to reduce music to its essentials.

The eighty-eight notes on a keyboard are produced by pressing white and black keys. The black keys are positioned slightly higher and farther back, as they hold all of the sharp and flat notes on the twelve-tone chromatic scale. This arrangement allows the natural notes to be played more easily, and make the non-natural notes more obvious.