The most common accordion in the United States is a piano accordion. Click on the
link to access a diagram.
The treble (piano) keys are played with the right hand. The standard accordion has 41
keys, 24 white keys and 17 black keys, ranging from a low F to a high A. Each key
controls two reeds. Sound is produced as the bellows push or pull air through steel
reeds. Each set of reeds is covered with a "leather" (which can be made of leather or
other synthetic material. In a piano and chromatic button accordion, the push and pull of
the bellows produces the same note. By contrast, in a diatonic accordion, such as a
Cajun or Tex-mex accordion, the push and pull produces different note (like a
By the 1880's accordions began to have sets of reeds in reed blocks. By the press of a
button or switch near the treble keyboard, a different set of reeds can be activated.
Reeds generally can produce a low, middle or high sound. A musette (vibrato) sound
requires two middle reeds tuned slightly apart. By 1955, the accordion manufacturers
agreed upon a standardized name and symbol for each set of reeds, as shown on the
Accordion Treble Switches
By the late 1880's the left hand buttons were commonly arranged according to the circle
of fifths with six rows of buttons. The second row (from the bellows) is the "fundamental
bass" [pronounced "bayse"] , i.e., C, G, D, D, A., E, etc. according to the circle of fifths.
The C button is usually marked by a depression or ridge. Often, the Ab button and the E
buttons in the fundamental row are also marked with a ridge. The row above the
fundamental bass (the row next to the bellows) is the counter-bass row, a major third
above the corresponding fundamental bass button. The next four rows below the
fundamental bass row are the major chord, minor chord, dominant seventh chord and
diminished chord. This arrangement is known as the "stradella" system. The bass
chords do not inlcude a 5th. Thus, a C7 chord is usually comprised of C-E-G and Bb.
The accordion generally omits the G (which is the weakest sound). Click on the link to
access a chart of the 120 button stradella bass system.
Accordion Bass Layout
Like the treble key reed blocks, different bass reed blocks can be activated by pressing
a switch or tab on the bass side of the accordion. A diagram of reed switches can be
accessed by clicking on the link below.
Accodion Bass Register Switches
While the "standard" accordion is comprised on 41 treble keys and 120 bass buttons,
there are many configurations allowing for a smaller and lighter accordion. Smaller
accordions may have 96, 72 or 48 buttons, often eliminating duplicate sounds. Piano
accordion keyboards may also come in varying widths of keys, allowing for smaller
Generally, an "air" button near the bass buttons can be used to quickly close the
accordion without generating a sound. An adjustable bass strap, found on the button
side of the piano accordion allows the user to move the bellows but have enough
freedom to allow the hand to reach the bass buttons.
Bellows are the heart of the accordion sound (i.e., the "squeeze box") which allow the
air to be compressed and released over the reeds to create the unique accordion