The Sheet Music Header
The header contains information you normally see on the first page of traditional printed sheet music. This can include the title and credits including composer, arranger and so forth. These are of course extracted from the MusicXML file and so whatever is included (or not) is displayed (or not). For example, not all files specify a title and so there may not be one displayed in large font on the top line. Sometimes the title is specified in the credits in which case it will be displayed on the second line in a smaller font.
If specified, the score's metronome value for beats per minute is displayed in the upper left of the header. If not specified, that header field is left blank.
SNapp displays the score's key signature in the upper right of the header. Along with it, the score's mode is displayed (major or minor) if the mode is specified in the MusicXML file. However, not all MusicXML files specify the mode (in fact most probably don't). In this case, SNapp displays both the Major and minor key signatures. The set of notes included in both keys is the same, it's just the starting point (the tonic) that is different (e.g., C Major and A minor). The key signature is only provided for informational purposes. The musician need not memorize the key signature in order to know how to play naturals, sharps, and flats, since the noteheads explicitly define them.
Staves and Grandstaves
SNapp displays only the staves specified in the score, so there may be a single treble staff, a single bass staff, or a grandstaff with both. This would apply to an individual instrument of any type or to a singer's voice.
The "beta" version of SNapp does not support the display of multiple "parts". A "part" can be an instrument or a singer's voice. SNapp implements the following approach for scores that contain multiple parts. Note that there is a bias towards the piano at this time.
A single part that has either treble only, bass only, or grandstaff is displayed correspondingly for any single instrument or singer.
For multiple part scores, only (the first) piano part is displayed.
For multiple part scores without a piano part, the first part encountered in the MusicXML file is displayed.
The display of staves and grandstaves is controlled by the Preferences as describe above. A musician can adjust these to make it easier to read directly from a device's screen. Different preferences might be chosen for printing purposes.