Definition and background:
Aerophone, Free Reed Instrument, Wind instrument; The accordion was invented by Friedrich Buschmann in 1822 in Berlin. He called invention the Hand'oline. In 1829, Cyrillus Damian of Vienna created another version of this instrument and gave it the name of accordion because of the addition of buttons, played by the left hand, that sounded chords.("Accord" is the French term for chord.) Eventually, the name accordion was used for all instrument of this type. It has been a popular instrument through the years with large organizations over the world created for accordion enthusiasts. It has been popular in many cultures as the main instrument in several musical genres. These include cajun zydeco from America, polka of Europe and America, Latino polka of Mexico, tango of Argentina, and classical transcriptions of European composers of the 19th and 20th centuries. There have also been several serious composers that have written works for the accordion including Peter Ilyich Tchaikovsky, Dmitri Shostakovich, Roy Harris, and Alban Berg. The accordion is a portable wind instrument consisting of two reed organs connected by a folding bellows. Expanding and contracting the bellows provides air to vibrate the reed organs producing the sounds. It is also known as a squeeze box because of this expanding and contracting of the bellows. There is a keyboard on the right side for playing melody notes and buttons on the left to sound bass notes and full chords. A second type of accordion contains buttons on both left and right sides which includes the concertina and Bandoneon. The keyboard on the right side of the accordion typically contains 41 keys but the smaller models can contain as few as 25. The full "concert accordion" will typically have four sets of reeds called treble shifts, one set tuned in unison, a second set tuned one octave higher, a third tuned one octave lower, and the fourth set, the tremulant, tuned slightly higher than unison. The left hand operates the bellows and each change of direction of the bellows will produce a new attack of the notes that are desired by the keys or buttons that are depressed. The speed of the expansion and contraction also effects dynamics and the shapness of the attacks. It also operated the bass buttons with the larger instruments having as many as 120 bass buttons with six rows of twenty buttons. There is also a button with no reeds operated by the left hand that allows the bellows to expand or contract without sounding any pitch. On this instrument, the fifth and sixth row (farthest from the hand) consists of the counterbass row and the fundamental bass row of buttons that sound individual low notes containing all twelve chromatic pitches. The fourth row consists of buttons that sound a major triad. The third row consists of buttons that sound minor triads. The second row consists of buttons that sound dominant seventh chords and the final row consists of buttons that sound diminished seventh chords. These buttons are arranged in the circle of fifths. These pitches can also be doubled an octave lower with the treble shifts (lower octave) selected. The accordion has a very rich, reedy and organ-like sound. The accordion has the ability to play single or multiple notes on the keyboard (right side) as well as chords on the left side. The tone quality of the melody notes can be altered by changing between the combinations of reeds (treble shifts) as discussed above. A universal system of labels has been given to these treble shifts for the composer to designate specific sounds. Table of Treble Shifts and Labels Unison only Unison & Lower Octave Lower Octave only Unison & Higher Octave Higher Octave only Unison & Tremulant Higher Octave & Lower Octave Unison, Higher Octave & Lower Octave Unison, Higher Octave & Tremulant Unison, Lower Octave & Tremulant Master (all sets) Additional notation is required to indicate the direction of the bellows. An arrow pointing to the left directs the performer to open the bellows and an arrow to the right directs the performer to close the bellows. An effect called a bellow shake is basically a rapid in and out movement of the bellows. The notation of "B.N." will end the effect indicating "bellows normal." Table of Bellow Markings Open Bellows Close Bellows Bellow shake Bellows normal B.N. The accordion is capable of a large dynamic range from very soft to very loud. Loud dynamic levels with several notes and full chords sounding require more air and cannot sustain the notes for more than a few seconds. Softer dynamic levels with fewer notes depressed can be sustained longer. The basic accordion keyboard range spans from F below the treble clef staff to the fifth space A above the treble clef staff. The treble shifts provide an additional octave higher and lower than the basic range. Both the counterbass and fundamental bass pitches begin at the D below the bass clef staff and go to the D in the bass clef staff. The chords (major, minor, dominant seventh, and diminished seventh) range from the E-flat in the bass clef staff to the D above the bass clef staff. Using the treble shifts, the fundamental bass and counterbass ranges can be extended from the D-flat five lines below the bass clef staff to the B in the treble clef staff. The chords can be extended from the G-flat in the fourth space below the bass clef staff to the F above the bass clef staff. See also concertina; [Ger.] Bandoneon. Also [Fr.] accord'on, [Ger.] Ziehharmonika [It.] fisarmonica.
For more information on the music term "Accordion" check out these other resources:
Wikipedia - Glossary of Musical Terminology
Virginia Tech Multimedia Music Dictionary
ORB -- Medieval Music Glossary