VHV will validate the structure and rhythmic syntax of Humdrum files before attempting to render them to graphical notation.

Syntax errors

When editing a Humdrum file in Verovio Humdrum Viewer, the ace editor automatically validates the Humdrum file structure as data is typed. If it detects invalid structure in the Humdrum content, the graphical music notation windows will be highlighted in pink, and an error message can be viewed by moving the mouse over any “x” boxes displayed in the line-number gutter to the left of the editor window.

Here is a demonstration of structural syntax errors:

Syntax errors
Structural syntax errors.

The first problem is that the spine was not split properly into two sub-spines. Adding *^ after line 2 will fix that problem:

Syntax error 1 fixed
First structural syntax error fixed.

Now there is just a single syntax error on line 8. Fix this error by adding two *v merge tokens to combine the subspines into a single spine again:

Syntax error 2 fixed
Second structural syntax error fixed.

Notice that the graphic notation is not highlighted in pink, which indicates that the data was rendered successfully. Also notice that when the graphic music is highlighted in pink, the last valid state of the humdrum data will be shown, and any new content added after the invalid structure was identified will not be shown.

Syntax warnings

Syntax warnings are shown as an exclamation mark in a yellow caution triangle within the line-number gutter on the left side of the text editor. These errors are non-critical, but should be fixed if preparing a score for public distribution.

Here is an example warning icon that appears on blank lines:

blank line warning
Warning icon displayed for a blank line.

If you move your mouse over the warning icon, and explanation of the warning will be displayed:

blank line warning message
Warning message for a blank line, viewable when mousing over warning icon.

End-of-spine syntax warning

The end-of-spine syntax warning is a special case where a warning message is displayed when a spine is not terminated properly using a *- token:

end-of-spine warning message
Warning message for missing spine terminator.

For command-line parsing of Humdrum data, this warning is an error in the file structure that will be identified by the humdrum command. However it is treated as a warning in VHV so that graphical music notation can be displayed while the data is being typed into the text editor. Remember to terminate the spine properly when finished entering the music.

Rhythmic syntax

Rhythmic syntax in VHV is also dynamically checked in a similar manner to the file structure. The error messages in this case are displayed on the line where the rhythmic error is noticed rather than on the line where the rhythmic error occurs (since it is not always possible to identify which spine has the rhythmic error.

Here is an example rhythmic error, where the data for the top staff of music contains a dotted quarter note instead of a regular quarter note:

rhythm syntax error
Rhythm syntax error.

Notice that the error is found on the 11th line, but the error is actually on the 10th line. Moving the mouse over the error icon will display an explanation about the warning:

rhythm syntax error warning
Rhythm syntax error warning.

This means that at field (column) 2 the rhythm is advanced an eighth note ahead of field (column) 1, since there is a dotted eighth-note instead of a quarter note in the second spine at line 10.

Fixing the rhythmic error allows the Humdrum data to be sent to the verovio toolkit for rendering into graphical notation:

rhythm syntax error fixed
Rhythm syntax error fixed.