A website for the serious amateur violin maker, restorer and tinkerer. A violin front and back (the plates) can be tuned using tap-tones. Use tap tones to adjust the 2 plates of a violin to get the best sound, the kind of sound you want, or make an instrument that is easy to bow.

This site has something for you if you are either making a violin or you want to improve  a low cost violin or viola.

By tuning the top & back plates you can get a good instrument that responds well to the bow and that can sound like a $1500 instrument.

post-25136-1224022475 Strad back graduation V1.1 smll1
tapping belly 2 sml

All you can ATE!

 A is for Arching,

   T  is for Tap-tones, &

      E  is for Edge-work.


‘Harrison’ Stradivarius violin plate thicknesses

email: webmaster @platetuning.org

 Last updated:                                        10th. March 2017                  Copyright  (C)                www.platetuning.org


   I hope this page will help those making their first 10 violins: to you everything is new and so who can tell good from bad?

      If I had to name priorities on how to make a violin I would  say “A. T. E.” :-

  • ‘A’ stands for arching:    it has to be right!
  • ‘T’ stands for Taptones, so the violin will sound good, and
  • ‘E’ stands for Edgework. Taptones do not measure the way the edges are cut, so the channeling and edge thickness (how it becomes the rising arch of the plate) has to be right because tap-tones do not measure plate edges properties at all well.
  •      There are people, perhaps even many people who regard tap tones as astrology for violin makers, just so much mumbo-jumbo. Once you have enough experience, and I mean many years handling the best violins along with training by professionals, you probably wont need tap tuning: flexing a plate and feeling the thickness profiles will do on its own. But, and it is a big but, those of us who do not have this experience and can never hope to get it need all the help we can get.

      Tap tones keep me and can keep us on the right track as they can help you create a violin with those 5 key body resonances in the right places!

The basics of good violin plate tuning or the tap-tones come down to this:-   

ThEdges 1ere are 5 key areas that need to be understood:-

(1) The plate edges    

       Unfortunately plate tap tones are hardly affected at all by the thicknesses of the plate edges, and yet these very edges matter because the plate is held firmly by the bouts and linings in the assembled violin 2. So take care with your choice of edge thicknesses, especially between the C-bouts on the back plate, and complete the edge thicknessing before tuning the plates. Never make the edges thin around the C-bouts.

   I recommend thicknesses of 2.7-3.0 mm an all edges (just before the plate meets the linings) and 3.5 mm around the C-bouts 4 for both belly and back plates. Better wood needs thinner edges.


(2) Moisture content (MC).

     The violin plates measured here have low moisture content (MC) at about  6%, which is normal for wood in a heated workshop in winter. All Mode 5 frequencies should be set up to 15 Hz lower with 12% moisture content (MC) when plates are tuned in summer.

(3)  The Mode 5 Tap Tones 1ring tones of both front and back plates.  Moeckel's data, belly & back Mode 5's V2.1 smll

        These are important characteristics of the violin plates as far as defining what the violin will sound like and how playable it is. They reflect your choice of plate height at the centre, the arching and edge work.

    (3a) The Mode 5 ring tones of back and front both need to be between 300 and 380 Hz. If they are not in this range then start again. The dynamics of the violin are from the belly of the violin, and power comes from the back1.

     It is important how much each plate ‘rings’ and what frequency that ring tone it is at.

     This is what Carleen M. Hutchins recommended 30 years ago, and more modern measurements and work have shown her conclusions were sound.

       The chart above right shows data for the belly (front) and back plates for 30 good Italian violins including 7 Stradivarius violins  [with thanks to Anders Buen and Maestronet]. It is quite difficult to discern a pattern from all this data but it does show you have a lot of freedom in choosing the tap tones of back and belly to make an excellent violin!

       There is a lot we do not know about this data, but what I do show from here on is that you can make consistently good violins by using plates whose tap ones are selected using plate tuning.Viable violin plates locus, Varnished, A1 = 462 Hz V2.82 smll

    (3b) The ring tones (Mode 5) can be chosen to give you the tone you want.

       To get a violin that will sound and play superbly then use the chart on the right1: click on it to open up the ’Viable Plate locus’ chart. This chart shows the back’s Mode 5 tap tone along the bottom (x) scale, and the belly’s tap tone (Mode 5) on the vertical scale (y).

      It is based on a new model (May 2015) I have derived to predict the key resonances (B1- and B1+) when the Mode 5 frequencies (tap tones) of back and belly plates are known.

      To make a violin for instance with ‘Orchestral’ tone (highly recommended, especially for a first violin) make belly and back plates with Mode 5 frequencies that fall somewhere in the dark green area. An example would be both back and belly plates with Mode 5’s at 345 Hz. There are a lot of choices of pairs of frequencies, but it is established practice to make the front plate or belly with a ring tone equal to or rather lower than the back.

      This chart is for varnished plates. Varnish will have added about 6 Hz to the belly’s Mode 5, but hardly anything to the back’s Mode 5 frequency.

      This is not law brought down by Moses from the mountain: but you will not go far wrong if you follow this!

     (3c) Choice of violin tone.

           Outstanding ‘Solo’ instruments’ have plates with Mode 5’s falling in the red area.  So what this shows is that if you want to make a ‘Solo’ toned violin you will need to make the 2 plates with ring tones up to 370 or 380 Hz if the wood you are using is both light and stiff.

    For an ‘Orchestral’ toned violin I suggest you make 2 plates whose Mode 5’s are between Plate samples spreadsheet Table of Deltas No 1, V1.91 smll340 Hz and 350 Hz and the point where the Mode 5 tap tones falls in the dark green area..

      A very good choice is an amateur violinist or ‘student’ tone: for a violin that is easier to bow, sounds ‘warm’ and is well suited to smaller rooms and chamber music. You will need to have a back and a belly plate at about  330 Hz (unvarnished, 6% MC). The intersection of the Mode 5 tap tones just needs to fall in the light green area. It will be easy to bow and a delight for chamber and pub music.

        There are 2 additional tables of values given on the right. Clckon them ato access the .pdf documents :-

    Table 1 will allow you to derive the expected B1- to B1+ ‘Delta’ (in Hz) for a pair of belly and back plates in .

    Table 2  allows you to select the back or belly Mode 5 frequency when you know one plate’s Modes 5 and the ‘Delta’ you need for a particular tone. The ‘Delta,Plate samples spreadsheet Table of Deltas No 2, V1.91 smll the difference between the violin body’s B1- and B1- body Mode frequencies should lie between 50 and 95 Hz.

      I have assumed a typical A1 violin body resonance around 460 to 467 Hz 1. If your violin's internal air volume (cm3), body length and the f-hole size are non-standard it will have a different A1 body mode frequency..   These charts assume that  Mode 2 = 0.5 x Mode5, that is they are octave plates.

    Chart: I have included a Chart (below right) that summarises how the Mode 5 of back and belly (free) plates can roughly predict the B1- and B1+, and therefore the important ‘delta’ between them, which is so important to a violin’s tone. It is not as easy to use however as the Tables above it.

    (3d) Real wood is never ideal.

      If the wood you use (spruce for bellies, maple for backs) is not the best thenB1- and B1+ for given f5.belly and f5.back smll that plate will usually turn out heavier than the reference weight given below.

         Once the violin is put together ‘in the white’, that is before varnishing, Stradivarius and many other makers used a technique of tuning the body resonances to exactly what he wanted by finishing the channeling and purfling after the violin was assembled as it affects these key resonances a lot.

       You can also make the plates a little too thick and then thin them ‘in the white’ by scraping or sanding the outside of the plates to get those resonances just where you want them, but this is not for your first violin! This is very hard to do. Start by walking before you run!

       Alternatively I use the tables given here to estimate how much to take off the belly and back when I remove the belly for adjustments! (Use weakened glue to glue on the belly then!)

    (3e) If you are making the plates from scratch

        Cutting the f-holes on a belly reduces the Mode 5 by about 2 semitones (2 x 6% = 12%, about 38 Hz), but the original Mode 5 frequency is then restored to the same (or to a slightly higher frequency) by installing the bassbar.

 (4)  The final Mode 2 frequency of each violin plate.     

      The Mode 2 frequencies should also be at or just below half the Mode 5 or ‘Ring tone’ frequency.

 I have assumed for instance that Mode 2 is 0.5 x Mode 5 frequency in all the charts above: i.e. they are octave plates. Having Mode 2 any higher than this serves no purpose and increases its weight. Many or even most good violins have Mode 2  at about 0.43 x  Mode 5.  The Mode 2 of a belly plate is less important to a violin’s tone than Mode 5, so just set it at just under half of Mode 5 frequency using the techniques I show on the arching and thicknesses page, but do not thin the wood between the C-bouts of the back plate too much! In this area generosity is good.


 (5)  A low plate weight is an extremely and VERY GOOD THING.

       That is providing the tap tones are not too low. There is less material to soak up the sound energy.

    This needs very good, carefully chosen wood. With the very best low-density wood a soloist-quality 4/4 violin finished belly will be less than 70 grams, and a back, believe it or not, will be less than 96 grams.

     More often a finished belly plate on a factory violin or ‘unselected wood’ will be about 75 to 85 grams, and a back plate about 115 grams and sometimes more.

    A low plate weight with high tap tones is a measure of the quality of the plate, but makes no difference to the choice of tap tone (Modes 2 and 5) you need to make an excellent violin!


 The ‘reference’ weight of each plate is as follows in Table 3 below 3.:   This includes the standard or reference weight of violin, viola, ‘cello plates, and includes the ‘Tenor Violin’, which has plates (but not bout heights) very similar to the 1/2 size ‘cello. This table may help you understand how good your plates are! For given tap tones low weight is good!


 [see Ref. 3 below]


Back length

in  mm.

Back length

in  inches (“)

Reference Belly weight.

in grams

Reference Back weight.

in grams

1/2 size violin





3/4 violin





4/4 violin   





15 1/4" viola





15 1/2" viola





16" viola





16 1/2" viola










'Cello, 1/4 size





'Cello,1/2 (half) size





Tenor Violin





'Cello, 3/4 size





'Cello, 7/8 size





'Cello 4/4 






1  This model is derived as a new model derived from Alonso Moral’s paper of 1984, and uses data from some 18 violins where both plate Mode 5 frequencies are known along with their B1- and B1+ frequencies. This includes the data published in Patrick Kreit’s book and website that gives the ‘deltas’ between these (A0), A1, B1-, B1+ body resonance’s we should look for in a first rate violin. The 3 coloured areas correspond to 3 different ‘Deltas’ (B1- to B1+ frequencies) in the final violin body that are 10 Hz apart. You will need to get Patrick Kreit’s book to get more details.

2.  See “The Art of Violin Making”  by Courtnall and Johnson and the chapter on plate tuning. Tap tones do not measure everything about a plate!

3.  This Table 2 is derived simply from taking the 2 known plate reference weights: violin and ‘cello, and assuming a straight power relationship between them.  So ....    plate weight = (plate length/reference plate length)^2.53       for each belly plate,  and ...       plate weight = (plate length/reference plate length)^2.31 for each back plate with suitable constants.    The plate shapes for all the instruments are assumed to be all very similar.

4. Figures from Patrick Kreit thickness data