Octave in the context of "Fret"

In music, monophony is the simplest of musical textures, consisting of a melody (or "tune"), typically sung by a single singer or played by a single instrument player (e.g., a flute player) without accompanying harmony or chords. Many folk songs and traditional songs are monophonic. A melody is also considered to be monophonic if a group of singers (e.g., a choir) sings the same melody together at the unison (exactly the same pitch) or with the same melody notes duplicated at the octave (such as when men and women sing together). If an entire melody is played by two or more instruments or sung by a choir with a fixed interval, such as a perfect fifth, it is also said to be monophony (or "monophonic"). The musical texture of a song or musical piece is determined by assessing whether varying components are used, such as an accompaniment part or polyphonic melody lines (two or more independent lines).

In the Early Middle Ages, the earliest Christian songs, called plainchant (a well-known example is Gregorian chant), were monophonic. Even into the twenty-first century, songwriters still often write songs that intersperse sections using monophony, heterophony (two singers or instrumentalists doing varied versions of the same melody together), polyphony (two or more singers or instrumentalists playing independent melodic lines at the same time), homophony (a melody accompanied by chords), or monody (a single melodic line with instrumental accompaniment) elements throughout the melody to create different atmospheres and styles. Monophony may not have underlying rhythmic textures, and must consist of only a single melodic line.

A barbershop quartet is a group of four singers who sing music in the barbershop style, characterized by four-part harmony without instrumental accompaniment (a cappella). The four voices are: the lead, the vocal part which typically carries the melody; a bass, the part which provides the bass line to the melody; a tenor, the part which harmonizes above the lead; and a baritone, the part that frequently completes the chord. The baritone normally sings just below the lead singer, sometimes just above as the harmony requires. Barbershop music is typified by close harmony—the upper three voices generally remain within one octave of each other.

While the traditional barbershop quartet included only male singers, contemporary quartets can include any gender combination. All-female barbershop quartets were often called beauty shop quartets, a term that has fallen out of favor. The voice parts for women's and mixed barbershop groups use the same names as those for male groups since the roles perform similar functions in the quartet although the vocal ranges may be different.

Musica enchiriadis is an anonymous musical treatise authored during the 9th century. It is the first surviving attempt to set up a system of rules for polyphony in western art music. The treatise was once attributed to Hucbald, but this is no longer accepted. Some historians once attributed it to Odo of Cluny (879–942). It has also been attributed to Abbot Hoger (d. 906).

This music theory treatise, along with its companion text, Scolica enchiriadis, was widely circulated in medieval manuscripts, often in association with Boethius' De institutione musica. It consists of nineteen chapters; the first nine are devoted to notation, modes, and monophonic plainchant.

A musical keyboard is the set of adjacent depressible levers or keys on a musical instrument. Keyboards typically contain keys for playing the twelve notes of the Western musical scale, with a combination of larger, longer keys and smaller, shorter keys that repeats at the interval of an octave. Pressing a key on the keyboard makes the instrument produce sounds—either by mechanically striking a string or tine (acoustic and electric piano, clavichord), plucking a string (harpsichord), causing air to flow through a pipe organ, striking a bell (carillon), or activating an electronic circuit (synthesizer, digital piano, electronic keyboard). Since the most commonly encountered keyboard instrument is the piano, the keyboard layout is often referred to as the piano keyboard or simply piano keys.

In Western musical notation, a key signature is a set of sharp (♯), flat (♭), or rarely, natural (♮) symbols placed on the staff at the beginning of a section of music. The initial key signature in a piece is placed immediately after the clef at the beginning of the first line. If the piece contains a section in a different key, the new key signature is placed at the beginning of that section.

In a key signature, a sharp or flat symbol on a line or space of the staff indicates that the note represented by that line or space is to be played a semitone higher (sharp) or lower (flat) than it would otherwise be played. This applies through the rest of the piece or until another key signature appears. Each symbol applies to comparable notes in all octaves—for example, a flat on the fourth space of the treble staff (as in the diagram) indicates that all notes notated as Es are played as E-flats, including those on the bottom line of the staff.

In music theory, a scale is "any consecutive series of notes that form a progression between one note and its octave", typically by order of pitch or fundamental frequency.

The word scale originates from the Latin scala, which literally means "ladder". Therefore, any scale is distinguishable by its "step-pattern", or how its intervals interact with each other.

In music, a pitch class (p.c. or pc) is a set of all pitches that are a whole number of octaves apart; for example, the pitch class C consists of the Cs in all octaves. "The pitch class C stands for all possible Cs, in whatever octave position." Important to musical set theory, a pitch class is "all pitches related to each other by octave, enharmonic equivalence, or both." Thus, using scientific pitch notation, the pitch class "C" is the set

Although there is no formal upper or lower limit to this sequence, only a few of these pitches are audible to humans. Pitch class is important because human pitch-perception is periodic: pitches belonging to the same pitch class are perceived as having a similar quality or color, a property called "octave equivalence".

In medieval music, ambitus (Ecclesiastical Latin: ['am.bi.t̪us]) is a Latin term literally meaning enclos[ur]e, and in Medieval Latin means the "range" of a melodic line, most usually referring to the range of scale degrees attributed to a given mode, particularly in Gregorian chant. In Gregorian chant specifically, the ambitus is the range, or the distance between the highest and lowest note. Different chants vary widely in their ambitus. Even relatively florid chants like Alleluias may have a narrow ambitus. Earlier writers termed the modal ambitus "perfect" when it was a ninth or tenth (that is, an octave plus one or two notes, either at the top or bottom or both), but from the late fifteenth century onward "perfect ambitus" usually meant one octave, and the ambitus was called "imperfect" when it was less, and "pluperfect" when it was more than an octave.

All of the church modes are distinguished in part by their ambitus. The plagal modes have the final in the middle of the ambitus, while the authentic modes generally go no more than one note below the final.

A setar (Persian: سه‌تار, pronounced [seˈt̪ʰɒːɾ]) (lit: "Three Strings") is a stringed instrument, a type of lute used in Persian traditional music, played solo or accompanying voice. It is a member of the tanbur family of long-necked lutes with a range of more than two and a half octaves. Originally a three stringed instrument, a fourth string was added by Mushtaq Ali Shah by the mid 19th century. It is played with the index finger of the right hand.

It has been speculated that the setar originated in Persia by the 9th century AD A more conservative estimate says "it originated in the 15th century, or even earlier."