Accordions from A to Z (Part 4, Tu to Z)

By David Tong

Playing the accordion is even more fun if you know how it works and what’s inside it.  It also helps when you set out to choose a new one.  This fourth article in the present series completes our accordion alphabet.


A very useful feature of the accordion is that no tuning or other attention is required for periods of years at a time. Mostly its initial shape and size determine the pitch of a given reed.  Provided it does not rust or collect a deposit from polluted atmospheres, the only detuning mechanism seems to be the very slow change in the properties of the steel due to the continual flexing.

Reeds are pre-tuned to pitch once they have been riveted to the reed plate.  Then final tuning is done after the reed plates have been fitted to the reed block and after the latter has been installed in the accordion.  This is because the pitch of a reed depends slightly on the air cavity surrounding it.

Test bellows

Test bellows

The bass or treble section is placed on the padded top of a bench-mounted bellows such as the one pictured and this is used to sound the selected reed.  After each trimming adjustment the assembly has to be lifted back onto the test bellows to sound the reed again to check the effect of the adjustment. 

The procedure takes a long time because of the large number of reeds involved.  It is laborious especially with large accordions, yet requires great care and precision, and lots of experience. 

Tuning Meter

Stroboscopic tuner

Stroboscopic tuner

Although some tuners claim to work entirely by ear, most use a stroboscopic tuning meter.  This works like the strobe disc used on now-obsolete record players. 
A disc with sets of concentric radial lines, one for each octave, rotates at a precise speed and is illuminated by light made to pulsate at the same rate as the note from the reed being tuned – the sound being picked up by a microphone and amplified.

Because of the stroboscopic effect the radials blur into a single line that rotates clockwise or anticlockwise, like wagon wheels at the cinema.  When the frequency is exact, the apparent rotation stops, so the reed is trimmed until the pattern is stationary.  Even very tiny errors (less than a cent) make the pattern rotate clockwise when the reed is sharp and anticlockwise when it is flat so this is an extremely sensitive way to detect tuning errors.

A knob calibrated in cents allows the instrument to be set sharp or flat from nominal tuning – the latter being based on A at 440Hz.  This knob is used when tuning tremolo and musette reeds that have to be offset from the clarinet reeds.
The tuning meter in the picture is fairly old-tech but works fine.  It has one strobe wheel and you select the desired note using a knob.  To save time, meters used in a production environment have twelve smaller wheels all spinning at once, one for every note.

Valves (Ventilli)

To stop air leaking past the inactive reed of each pair, long rectangular one-way valve flaps, or ‘ventilli’, are used.  They are made from a special grade of soft floppy leather (pelle) cut along the grain, or from mylar plastic. 

One end of the flap is glued to the reed plate in the riveted area on the opposite side to the reed, and the other end lies free.  To stop the larger ones sagging under their own weight a narrow metal ‘helper’ spring (the contrapelle) is fitted to press them lightly against the reed plate.

Leather valves last for years when used in non-humid conditions, but are prone to mould in wet conditions.  Mylar valves are safe from mould and last a long time in clean air, but are reputed to collect sticky deposits in polluted atmospheres.

Often manufacturers use leather for the larger reeds and plastic for the smaller ones.  The smallest reeds do not need valves because the air leakage around them is so small anyway.


Each complete set of reeds is called a voice or a register.  The number of voices fitted to an accordion has a big impact on its size, weight, and cost.

On the treble side, a ‘complete set of reeds’ means ‘a pair of identical reeds for each individual note on the keyboard’, one for each bellows direction.  On the bass side, each voice requires a pair of reeds for each of the twelve notes required to span a major seventh, e.g., from G to F#. 

Most contemporary accordions have four or five bass voices, and from two to five treble voices.  An accordion with three treble voices and four bass voices is described as having ‘3/4 voices’.


Weighing an accordion

Weighing an accordion

Although handy enough, most bathroom scales are useless for weighing accordions because they are very inaccurate.  While weight watchers and accordion manufacturers may welcome optimistic scales, accordionists do not.

A better solution is to get one those spring balances used by anglers, or more recently one of those designed for weighing suitcases.  Then all you need is something to hang it on and you are in business.  The photograph shows a Beltuna Studio III 72-bass being weighed while daringly suspended from a tree branch.


The weight of an accordion is important.   If it is too heavy it will be awkward to carry about, and it may become just too much trouble to take it with you.  It may also be too cumbersome to play properly.  Even worse, you may risk damaging yourself by lifting and using it.

In recent years people have become much more aware of health matters and maybe this is why we are now more interested in the weight of the accordions we play.

It has taken a long time for the Italian accordion industry to realise that weight is an issue.  While some manufacturers have responded by improving designs and providing accurate data, others apparently prefer to risk their reputation by quoting misleadingly optimistic weights in their literature. 

Nevertheless, full-size reed blocks are heavy and so a fully equipped 120-bass 5-voice instrument with real reeds will never be exactly ‘light’.  So a second way to ‘go light’ is to reconsider whether you really need all those voices, or to play in the less common keys.

Well Tempered Scale

When notes sound really nice together their frequencies are usually related by simple whole number ratios such as 3/2 (a fifth), 4/3 (a fourth), 5/4 (a major third).  The smaller the numbers in the ratio, the more satisfying the sound. Pythagoras and many others knew this long ago. 

Looks good but depends on the well-tempered scale

Looks good but depends on the well-tempered scale

By choosing notes on this basis scales were developed over many years and gradually became more complex.  Eventually it became customary in Western music to divide the octave into twelve notes to give what we call the chromatic scale.  Starting at C, for example, these notes are called C, C#, D, D#, E, F, F#, G, G#, A, A#, B, and each pair of notes are separated by a ‘semitone’. 

When the individual notes are chosen to preserve the desirable whole number ratios it turns out that the frequency ratio between the pair of notes in each of the twelve semitones is nearly the same, but not quite. 

When people made organs and other keyboard instruments they sounded fine provided the music remained within the musical key to which the instrument was originally tuned, say C major.  But problems arose when they tried to play such an instrument in other keys – that is, in scales based on one of the other eleven notes in C major other than C itself.

The problem is that while the frequencies of the ‘ideal’ notes in the various scales are all fairly close to those of the twelve original notes, they do not correspond exactly.  So you really need separately tuned notes for B-flat and A#, and so on.  However this would make the instrument and keyboard so complicated as to be impracticable and the solution requires some kind of compromise. 

After much experimentation people decided that the best compromise is actually the simplest.  You split the octave up into twelve equal intervals.  That is, you make the ratio of the frequencies of each adjacent pair of notes (each semitone) identical.  The resulting set of notes forms the ‘equal tempered’ or ‘well tempered’ scale.  Looked at from the point of view of each musical key, many of the resulting intervals are slightly off-tune.  However the remarkable thing is that the errors are small and shared out pretty evenly.  They are small enough to be ignored by most people most of the time. 

The benefits of being able to build keyed instruments that are not unreasonably complex, and to modulate freely from any key into any other, are considered to outweigh the drawback of most intervals being slightly mistuned.

‘Wet’ or ‘Dry’

This refers to the amount of detuning in Musette or Tremolo Tuning.  ‘Dry’ means ‘hardly any’ (say 5 cents) and ‘wet’ means ‘quite a lot’ (say 20 cents or more).


Wood of many varieties is still an important constituent of accordions.  It is used for body shells, reed blocks, keys, sounding boards, tone chambers, and pallets.

The type of wood used for the items associated with sound production seems to affect the sound quality to some extent.  However objective comparisons are difficult to make and there seems to be no reliable published information about the principles involved in selection.

A demand for lighter instruments has led to softwood replacing hardwood for various components.  Reed blocks are often made from pine when the reed blocks are fixed with wax and out of a harder wood when pinning is used.

Wrist Strap

Wrist strap adjuster

Wrist strap adjuster from the inside of the instrument

This is an adjustable leather strap on the bass section through which you pass your left wrist when playing the instrument.  Without this you could push the bellows in but not pull it out again.

All wrists are different, so all except very low-cost instruments provide a knurled wheel to adjust the tightness of the strap.  In the event that the base plate has to be removed the wheel can be fully unscrewed to release one end of the strap. 

The photograph shows an inside view of the knurled wheel and the threaded fitting on the end of the wrist strap on a Beltuna Prestige model.