Perfect fourth in the context of "Organum"

The violino piccolo (also called the Diskantgeige, Terzgeige, Quartgeige or Violino alla francese and sometimes in English as the Piccolo Violin) is a stringed instrument of the baroque period. Most examples are similar to a child's size violin in size, and are tuned a minor third (B♭₃–F₄–C₅–G₅) or a fourth higher (C₄–G₄–D₅–A₅). The most famous work featuring violino piccolo is the first Brandenburg Concerto of Johann Sebastian Bach.

The best-known violino piccolo is the Brothers Amati example in the National Music Museum in Vermillion, South Dakota. By modern measurements, the body is 1⁄4 size, the neck 1⁄2 size, and the head corresponds to that of a 3⁄4 size instrument. The string length is the equivalent of a 4⁄4 violin stopped a minor third from the nut, which corresponds with its normal tuning of a third higher than a 4⁄4 violin. It's notated in E flat. This Amati violin also has fingerboard widths similar to that of a 4⁄4 board cut a third shorter, which in view of the other measurements implies a clear conceptual relationship to the 4⁄4-sized violin.

In music theory, a tetrachord (Greek: τετράχορδoν; Latin: tetrachordum) is a series of four notes separated by three intervals. In traditional music theory, a tetrachord always spanned the interval of a perfect fourth, a 4:3 frequency proportion (approx. 498 cents)—but in modern use it means any four-note segment of a scale or tone row, not necessarily related to a particular tuning system.

In music, an octave (Latin: octavus: eighth) or perfect octave (sometimes called the diapason) is an interval between two notes, one having twice the frequency of vibration of the other. The octave relationship is a natural phenomenon that has been referred to as the "basic miracle of music", the use of which is "common in most musical systems". The interval between the first and second harmonics of the harmonic series is an octave. In Western music notation, notes separated by an octave (or multiple octaves) have the same name and are of the same pitch class.

To emphasize that it is one of the perfect intervals (including unison, perfect fourth, and perfect fifth), the octave is designated P8. Other interval qualities are also possible, though rare. The octave above or below an indicated note is sometimes abbreviated 8 or 8 (Italian: all'ottava), 8 bassa (Italian: all'ottava bassa, sometimes also 8), or simply 8 for the octave in the direction indicated by placing this mark above or below the staff.

A suspended chord (or sus chord) is a musical chord in which the (major or minor) third is omitted and replaced with a perfect fourth or a major second. The lack of a minor or a major third in the chord creates an open sound, while the dissonance between the fourth and fifth or second and root creates tension. When using popular-music symbols, they are indicated by the symbols "sus4" and "sus2". For example, the suspended fourth and second chords built on C (C–E–G), written as C and C, have pitches C–F-G and C–D-G, respectively.

Suspended fourth and second chords can be represented by the integer notation {0, 5, 7} and {0, 2, 7}, respectively.

E♭ (E-flat) or mi bémol is the fourth semitone of the solfège.

It lies a diatonic semitone above D and a chromatic semitone below E, thus being enharmonic to D♯ (D-sharp) or re dièse. In equal temperament it is also enharmonic with F (F-double flat). However, in some temperaments, D♯ is not the same as E♭. E♭ is a perfect fourth above B♭, whereas D♯ is a major third above B.

The Ionian mode is a musical mode or, in modern usage, a diatonic scale also called the major scale. It is named after the Ionian Greeks.

It is the name assigned by Heinrich Glarean in 1547 to his new authentic mode on C (mode 11 in his numbering scheme), which uses the diatonic octave species from C to the C an octave higher, divided at G (as its dominant, reciting tone/reciting note or tenor) into a fourth species of perfect fifth (tone–tone–semitone–tone) plus a third species of perfect fourth (tone–tone–semitone): C D E F G + G A B C. This octave species is essentially the same as the major mode of tonal music.

The musical system of ancient Greece evolved over a period of more than 500 years from simple scales of tetrachords, or divisions of the perfect fourth, into several complex systems encompassing tetrachords and octaves, as well as octave scales divided into seven to thirteen intervals.

Any discussion of the music of ancient Greece, theoretical, philosophical or aesthetic, is fraught with two problems: there are few examples of written music, and there are many, sometimes fragmentary, theoretical and philosophical accounts. The empirical research of scholars like Richard Crocker, C. André Barbera, and John Chalmers has made it possible to look at the ancient Greek systems as a whole without regard to the tastes of any one ancient theorist. The primary genera they examine are those of Pythagoras and the Pythagorean school, Archytas, Aristoxenos, and Ptolemy (including his versions of the genera of Didymos and Eratosthenes).