The key signature is an aggregation of sharps of flats placed on a staff that specifies a key or tonality to be used on that staff. Any natural note following such a key sharp or flat will have its pitch altered accordingly. These sharps or flats are not to be confounded with accidentals, which are notes whose pitch has been altered from the original pitch given by the key. Conventionally, there are 30 musical keys, ranging from C♭ major/A♭ minor to C♯ major/A♯ major.
The key signature edit dialog Edit
The first item in this dialog is a preview area, where the key signature is shown with the parameters given by other items in the dialog. In addition to the key signature, a clef and a time signature is drawn, in gray color if they are not active or visible in the current bar which will contain the key signature (change), and in default color otherwise. The preview area contains a drop-down menu with a list of all conventional keys that are used in music notation, ordered from the key with most sharps to the key with most flats. By choosing a selection from this list, the key automatically change to the selected one. Alternatively, on the right there is a set of controls for defining the key manually, by selecting notes to be either affected by a flat (left radio button), sharp (right radio button), or stay unaffected (middle radio button). This way, it is possible to form an unconventional type of key, useful for instance when writing modal music in an easy way; even if conventionally, modes do not use key signatures, but rather accidentals, a key signature tool can still be used as a helper: firstly the mode is set up by the use of an unconventional key, and after the music is finished writing, the key is disabled, while notes remain at their altered pitch, using accidentals.
To show or hide the key signature for a particular reason, you can use the "Show key signature" checkbox. When hidden, the key signature is displayed in the preview area as colored in grey.
Another way to choose a key is by using the "Base note" field, which accepts any note name as a tonic (use # for sharp and b for flat), and has a major/minor switch. Note that to pick for example the key of F minor, you must first select the minor switch and then type F in the "Base note" box, because the other way around would automatically switch the tonic name to the relative variant (as in the following scenario: user types F in the "Base note" field, presses "minor", and now the base not has changed to D minor, which is the parallel key of F major).
When a key signature is applied on a staff which further contains other key signatures, there are two ways of interaction between these: applying the current key until the next key change (done by having the "Apply changes to the end of tune" checkbox disabled), or using an additive system in which the following keys contain the number of sharps or flats from the current key, which are added to their respective sharps or flats. For example, if the current key contains 3 flats and the following one 1 flat, the later key will now hold 3+1=4 flats. If a sharp meets a flat, subtraction occurs.
If the key signature comes before notes that are already on the staff, a number of choices can be made from the "Transpose" list:
- None - Notes remain on their previous pitch, without being altered by the new key. If necessary, accidentals are applied
- Transpose up - Notes are transposed up so that the sequence is not altered. The easiest way of transposing a tune in any wanted key
- Transpose down - Similar to "Transpose up", but this time, notes are transposed to the new key by lowering their pitch
- Don't change notes graphical location - Notes remain where they are graphically, which means that changes in pitch may occur
Generally, a key change is global for all instruments in the sore. This is however not a necessary happening. In the "Apply to" list, the following choices can be made:
- The staff only - The key only applies to the current staff, other staves remaining in their respective keys
- All staves (absolutely) - The key is applied to all staves
- All staves (relatively) - The key is applied to all staves in a relative manner When another staff has a previous key different from the previous key on the current staff, the procedure described for "Apply changes to the end of tune" is used
- Selected staves (absolutely) - The new key is set to the staves that are included in the selection range
- Selected staves (relatively) - The new key is set to the staves that are included in the selection range in a manner identical to the one used in "All staves (relatively)"
Finally, the color of the key signature can be adjusted.