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Accordion encyclopaedia

Accordion encyclopaedia

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Concerning the accordion there are many non self-explanatory terms, we try in our accordion encyclopaedia  to describe some terms in an understandable way. This encyclopaedia is under progress. We are open for suggestions and if you have questions you are also welcome to contact us.


  1. Bellow
  2. Bellow strap
  3. Bass accordion
  4. Bass strap
  5. Bass systems
  6. Cassotto
  7. Housing and surface
  8. B-System and C-System
  9. Helicon basses
  10. Reed chambers
  11. Tone colour
  12. Converter and arrangement of the converter
  13. Air button
  14. Air consumption
  15. Octave and double octave tuning
  16. Registers
  17. Shoulder straps
  18. Reeds
  19. Reed block
  20. Tremolo tuning
  21. Valves
  22. „Weltmeister“ special cassotto

Bellow (also pair of bellows):

The bellow as the middle piece links the treble side and the bass side and is fixed on both of them with pins. By pushing or pulling the bellow creates an airflow which is also called „playing wind“. The bellows are produced suitable for the housing size and made of special cardboard. The only metal pieces on the bellow are the so called „corner protectors“ that are pressed onto the board after the edges have been trimmed. Due to it's material the bellow is one of the expendable parts of the accordion. The pleats all have the same depth. Number and depth depend on the instrument. The bellow has to be tight so that the internal air can not escape. For further protection slim stripes of synthetic leather are pasted on the pleats of the bellow. These slim stripes vary in colour correspondent to the instrument and are aligned exactly and in standardized length.

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Bellow strap:

The function of the bellow strap is to keep the bellow locked. It is very important to secure the bellow with the strap while carrying or storing the accordion to protect it from damage. The bellow straps are normally to be found on top and at the bottom of the case.

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Bass accordion:

Bass accordions are mostly played in accordion orchestras. These instruments have got the bass tones on the treble side. The sound of the bass accordion is generated by special HELIKON reeds that make it sound considerably deeper than the normal accordion. The range of the Weltmeister Basson for example reaches from C to c''. On the left side there are no reeds – it is just required to generate the air stream.

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Bass strap:

The bass strap is placed on the bass side of the accordion. It supports the left hand while playing and enables to open and close the bellow.

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Bass systems:


The free bass makes it possible to play melodies on the bass side in the correct tone pitch contrary to the popular Stradella bass system. The arrangement of the bass side correlates inversely to the arrangement of the treble side of a button accordion (B- and C- system). Converter types enable to switch between free bass and standard bass in a fast and easy way.

Stradella-Bass (fundamental bass)

The Stradella bass system (manual-II-bass) is the most used system in the bass side of accordions. This is why it is also called standard bass. This bass system enables easily to play root notes and major 3rd notes as well as the most common chords. The bass tones are vertically set up in quints and horizontally arranged in major, minor, seventh and flat seventh.

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A cassotto accordion is not recognizable from the outside. The so called cassotto chamber can be imagined as a passive filter which lowers particular frequencies in the higher tone area: they are muted. Others are strengthened by resonance: they are louder. They are sounding warm and mild. An instrument including a cassotto differs fundamentally from a normal one. Accordions with a cassotto are mostly used by professionals; they are higher in quality.

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Housing and surface:

The way of constructing the instrument does not influence the quality of sound that much. However the size of the free interior volume does. Sound level and tone colour depend on it. The corpus is to be built solid and light. Spruce wood is traditionally used as well as other types of solid wood. Multilayer wood is also applied because of it's good acoustic results.

Before 1920 the surfaces of the housing were treated like wooden surfaces in general. In 1920 – when the first plastics were fabricated – the celluloid covering became popular. Nowadays the producers often replace this technique with special eco-friendly multilayer coatings. Equally fashionable are solid wood instruments with a clear coat surface. Nowadays colour and design are mostly chosen by the musician himself and can be adapted to his individual conceptions.

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B-System and C-System:

Variable systems are only existing among the button accordions. This is due to regional conditions in the past that led to a different arrangement of the treble side.

Thereby the C- and the B- system emerged, named after a tone which is only to be found in the first row. Here it is decisive whether the order of half-tones increases from the outside or from the inside.

At the B-system button accordion – in German speaking countries also named the H-Syste, – the half-tones rise from the inside to the outside. Here the B is in the first row. B-system instruments are also called „instruments with Norwegian arrangement“. It is common in Norway, Russia, Belgium and Serbia.

At the C-System button accordion the half-tones rise from the outside to the inside. Here the C is in the first row. This grip system is also known as the Italian or Swedish arrangement. The C-System is preferred by French players and is very popular in France.

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Helicon basses:

The helicon bass is the characteristic feature of the Styrian Harmonica. The reeds which are responsible for the fundamental bass create a particular distinctive sound that reminds of the brass instrument Helicon. Helicon basses are very favoured in the folklore music of the alp regions. Extra long and big reeds generate this typical and special sound of the Styrian Harmonica. They are classified into single and double helicon reeds. Also some chromatic accordions can exhibit such ultra-large reeds such as for example the Weltmeister Monte Helicon.

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Reed chambers:

Located in the reed block are chambers that lead the playing wind to the reeds. The so called tone hole – closed by a valve cap – links the reed chamber with the outside area. When the accordion player press a key the valve cap opens, the playing wind flows through the reed chamber and makes the reed sound.

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Tone colour:

Concerning the tone colour the accordion has an exceptional position because the sound is generated directly on the reeds. The important thing is that the response time of the tone tongue is to be preferably short. Not only the existence of certain tones matters relating to the evaluation of the tone colour; likewise the oscillation amplitude of each tone is very important, because that leads to the different tone colour of identical tones. The oscillation amplitude is defined as the highest distance from the rest position that the oscillating tongue can have. The tone colour is related to the tuning of the instrument and it ranges from a „slight tone tuning“ to a „sharp tremolo“.

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Converter and arrangement of the converter:


During the development of the accordion it more and more turned out that it was quite hard for the musician to play a free bass instead of the standard bass or even in addition to it. Caused by this issue switchable bass mechanics were invented. The switch mechanism which was used to switch between both bass alternatives had been called „converter“. Using this converter bass on the left side (bass side) of the accordion, it can be switched from Stradella to free bass. This enables the musician to play melodies on the buttons that are normally used for accompany chords. Just the accord buttons can be converted – the single bass buttons can not. 

The converter bass has – compared to the standard bass – further keys for changing the manual. Converters are complicated constructions and vary particular from company to company. Despite the plenty of types the basic principle is always the same. Due to the special mechanics the converter instruments weigh some more. Because of the converter mechanism there are no additional reeds necessary.

A converter's button arrangement

A converter instrument can either have a C- or a B-system arrangement. The example for this arrangement is the chromatic accordion. The difference is that the key arrangement is arranged mirror inverted. An exception in this context is the Russian Bajan. The key arrangement indeed is mirror inverted, but the deepest tones are below.

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Air button:

In general the air button is located sidewise on the bass side. Some manufacturers affixed it as highest bass button. This can be found especially at older accordion types. The function of the air button is to open a valve which enables the bellow to be opened and closed silently.
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Air consumption:

While pushing or pulling the bellow leads the air inside the accordion to the reeds. Thereby an air space separates the oscillating tongue from the frame plate. To avoid marginally air ways that would decrease the amount of playing air this gap has to be as small as possible. This minimal distance between tongue and frame plate is both essential for a high quality tuning plate and a good sound. A high loss of air leads to more bellow movements: a higher expenditure of energy for the musician is the result. Besides the reeds for higher tones only response by higher pressure or pull. Bigger and mostly instruments with 4 reed ranks (mainly solo instruments) always have high quality reeds.

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Octave and double octave tuning:

Octave tuning:
Octave tuning means that there is a standing row of tones at intervals of one octave upward and downward to the fundamental note.

Double octave tuning:
If - beside the deep octave - also the higher one is to be used this connection is called double octave tuning.

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There are two types of registers.

1. treble register

2. bass register

By pressing the register keys the accordion player has the possibility to switch between different tone colours. For various types of music special sounds are required, such as violin/musette, oboe or cello. These tone colours are generated by the combination of the reeds also named reed ranks. The number of reed ranks determines the plenty of sounds the accordion has. The combination of the reed ranks is mostly illustrated by dots in a tripartite circle. The treble and bass registers can be switched by a trigger switch. Another alternative is a chin register which enables the player to switch the tone colour fast and without breaking the flow. These chin registers are often found in soloists' instruments. Some very few accordions also have a hand gear on the back of the treble side.

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Shoulder strap:

The shoulder strap stabilises the accordion and keeps it in the right position while playing. When the straps are being fixed there should be noticed that the strap for the right shoulder is shorter. Shoulder straps are produced in different lengths that are appropriate for children and adults. Furthermore the length is adjustable. Shoulder straps can vary in their width – there are softly padded luxury models that can have a width up to 9 cm. Such straps are best for playing while standing. Because of the width of the straps the weight of the accordion is scattered equally on both shoulders and due to the soft cushion the straps lie comfortably on them.

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The reeds are the core of each accordion. Therefore the quality of the reeds is eminently important. No other building activity could correct this quality – so it determines the practical value of the instrument in terms of the acoustic: an accordion for high musical requirements needs high quality reeds.

Three kinds of reed tongues are differentiated:

  • „mechanics“
  • „tipo a mano and „dural“
  • „a mano“
The „mechanics“ are those on the lowest quality level. They are mainly built into beginner's instruments and the reed tongues are produced by special machines. The sound of those tongues is duller and they have a range of disadvantages: the air consumption is high, the dynamic amplitude is poor and the tongues response insufficiently.

„tipo a-mano“:
The „tipo a-mano“ reeds are of middle quality (the „durals“ are the lower middle level). Differences to other quality levels are the riveting of the tongues and the accuracy concerning the manufacture. The treatment is often manual what led to the term „tipo a-mano“ (like handmade). So the reeds and the channels are reworked by hand which guarantees a good quality. The sound is mellow and bright, the air consumption is lower and they have a good dynamic amplitude.

„a-mano“ (mostly handmade):
These reeds are high class and are often named professional. Different from the „tipo a-mano“ ones the „a-mano“ ones are made from a slim steel strap. Even if there is just little pressure on the bellow the reed response easily. They are loud and have a brilliant sound. Their feature is a low air consumption caused by the perfect fitting accuracy of reed and frame plate. -

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Reed block:

The reed block can be made from wood or plastic - those production materials are equitable. The reed block with the reeds waxed on it belongs to the acoustic module of the accordion. It is split in so called reed chambers, that lead the air to the reeds. When the player pushes the bellow the air streams through reeds, reed chambers and tone holes from the interior to the outside – while pulling it goes the other way around. The tone hole is the link between the tone chamber and the surface broaching. It is locked by a valve flap. When the musician presses a key the valve flap is lifted and the playing wind makes the reed sound.

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Tremolo tuning:

The tremolo is an acoustic generated sound effect. It occurs when several reed tongues with slightly different tone pitches are oscillating together. This can be reached with one or two so called slight tones that sound additional to the fundamental note. With two tones involved one of them can be tuned below the fundamental note and the other one above. So alltogether three tones are sounding. This effect is also called Musette. Both player and listener do not notice two different floating tones but a more resonant sound. The stronger the floating is the stronger will be the tremolo.

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Valves mostly consist of leather and are fixed on the reeds. By means of these valves the airflow is cut off. Without valves and also with damaged valves an accordion can still be played but the air consumption would be much higher and also the playing would be more exhausting. A slightly change of tone pitch could occur as well.

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„Weltmeister“ special cassotto:

The cassotto (374 and 414) by „Weltmeister“ has got a special construction that was developed in Klingenthal. All reed ranks are arranged parallel like in a normal accordion. The cassotto effect is generated below the treble cover by a small „canopy“. This forms the cassotto space and a good cassotto-like sound can be reached. This construction is also called „Klingenthaler special cassotto“ or „filling cassotto“.

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