Tonalities and transposing instruments

Music notation software have solved most transposition problems. However the choice of a piece tonality according to a transposing instruments panel remains an  issue; so does the choice of a transposing instrument according to the tonality of the piece.

Transposition is a simple transfer of the fifths cycle.Let’s imagine a sliding rule:The fixed (yellow) part reads tonalities of the piece while the sliding (blue) part reads the instrument tonalities.

So willing to write an obsolete Db piccolo part for an Bb (2b) melody

I place the instrument C facing Db(piccolo tonality) on the fixed part ;to Bb (piece tonality) tallies (A) instrument(blue) tonality.



This needless  method for a single instrument becomes a  precious tool  when several  transposing instruments are involved.

First of all it should be reminded that the writing confines tonalities  to 7 accidentals(From  Cb(7b) to C#(7#)) in order to keep a  relative legibility; Beyond  those limits we  use enharmonic writing




« Forbidden » zones are in red but enharmonic choice  is also advisable  if an easier alternative tonality is available.

For  example , let’s take an  Ab Maj (4b) piece

For an A  clarinet the chart reads     7b  key signature

The best choice would be to switch to a Bb clarinet (2b)


But ,should we use an A clarinet for any reason ,we ‘d choose the  B Maj (5#) enharmonic writing.

Below is a correspondence chart

Neglecting the classical  double flats/sharps notation we  suppose an unlimited number of flats/sharps instead.

The result is always  12.



Double sharps equivalence



Notice the reverse direction of increasing flats and sharps