Key signature

Music theory reminder

The key signature enables you to define, within a score, a change of tonality, i.e. which scale is used to play the part.
Here is the list of all notes which can be played within an octave:

For the D major scale, that sequence of intervals gives a scale made of semitones 3 (root note), 5, 7, 8, 10, 12 and 14. Semitone #14 is in fact the 2nd semitone of the next higher octave.
Thus, it gives the D major scale: D, E, F#, G, A, B, C#.

In a score, if only the notes belonging to the scale of D are used, then all Fs and all Cs will be sharped. To make the notation less cluttered, these two sharp symbols are drawn only once, just after the clef symbol. This informs the performer of the key being used, and in so doing, the default accidentals (notes with sharps or flats).
To determine which key is used in a score (or a part), just count the number of sharps or flats drawn after the clef:

Generally, key signature changes apply to all staves in the score. Some instruments such as the clarinet, saxophone, trumpet or horn do not play the note actually indicated on the score, however, but a note shifted up or down by a given number of semitones.
They are called "transposing instruments".

Tip: In the software, to define a staff for a transposing instrument, use "Staff>Apply transposing instrument" or the option "Apply transposing instrument" in the staff contextual menu .

Note: The software extends the notion of transposing instrument to any instrument which does not play the note exactly as written. Thus, instruments like the piccolo or bass, which are not strictly speaking transposing instruments because they simply play the written note shifted by a given number of octaves, are included in the same option.

Location

A key change is always positioned at the beginning of a bar.You can specify a change of key signature at any bar in the score.
For example, a staff can begin in the key of C major, and then switch to F major a few bars later.

Editing

Global editing:
To change the global key signature of a score, select "Score>key and time signature". The key signature selection box opens.

Local editing:
A dedicated tool palette ("Window>Clef & signature tools") is available. It contains the key signature change tool, as well as tools for changing clef and time signature.
Select the key signature change tool (icon with sharp symbols on a staff) and click on a bar. The key signature selection box opens.

Selecting a key signature

In the selection box, choose the "key signature" tab. In the upper portion of the window, you can see a preview of the key signature you are defining.

By using the scroll bar you can add sharps and flats to, or subtract them from, the current key signature. Advanced users can also define custom keys by using buttons on the right, and defining the root note in the bottom field.

The "visible key signature" check box enables you to define whether the key signature is displayed or not. To ensure that your score remains readable, however, avoid setting invisible key changes.

The key signature display mode defines whether natural symbols are used to cancel the previous key signature or not.

The Propagate change till the end of tune check box enables you to transpose all key changes following the one you are setting. For example, if you switch key signature from C to D, all following key signatures will be increased by two semitones. In that case a G key signature (one sharp) later in the tune will be transformed into A (three sharps).

At the bottom of the window, pop-up menus enable you to select:

• The transposition to apply to notes when a new key is inserted into a score.
Notes following this key change can be:

• Not transposed: in this case, their screen location changes so that they play the same pitch as before.
• Transposed up: they will play in the new key, at a higher pitch than before.
• Transposed down: they will play in the new key, at a lower pitch than before.
• Graphically unchanged: they will stay at the same graphical location on the staff (but they may not sound at the same pitch as before)

• Which staves the key signature will be applied to.
It can be the current staff only, all staves in the score, or only selected staves.
In the two last cases, you can select whether the change is made in absolute or relative mode.
In absolute mode, the key change is applied as-is to other staves.
In relative mode, the key change is applied taking into account any key difference between the two staves (due to transposing instruments).  See below for more information. In case of doubt, select relative mode.

Absolute and relative mode

As described above, a key change can be applied absolutely or relatively.

When applied absolutely:

The new key change is inserted "as is" in all the required staves, i.e. all staves will play the same key at the same time. This is the general case for all pieces of music, except when using transposing instruments. Key signatures for these instruments are shifted a given number of semitones from the regular key. Because of this, applying the same key signature to all staves, including those playing transposing instruments, will result in erroneous keys for these instruments.

The program calculates the difference in semitones between the root note of the current key (at the location you clicked on) and the new key you want to insert. This difference is then applied to the key signature at this bar for all required staves. Transposing instrument key offset is then kept.
For example, if you have a first staff with a D key signature and another staff in G; inserting an  E key signature in relative mode on the first staff will result in:
- The difference between old and new keys is E-D = 2 semitones
- The first staff key is raised by two semitones: D+2 semitones = E as requested
- The second staff key is raised by two semitones: G+2 semitones = A key
Be careful, however: if you use custom keys, the program is not able to shift them up or down (it is impossible to determine whether accidentals must be added, or where). If such key signatures are present in your score, only their root note will be transposed as requested, and the accidentals will not be changed.


In summary: It is not recommended to use absolute key change mode on staves playing a transposing instrument. On the other hand, relative key change mode will not calculate new accidentals for existing custom keys.