Ignore/Remove percussion clefs when preprocessing MusicXML files

[napulen]

It seems that when a MusicXML file has a percussion part, the content of that part will be interpreted as nonsensical pitch content

{0.0} <music21.instrument.Instrument 'P10: Drumset: Acoustic Bass Drum'>
{0.0} <music21.stream.Measure 1 offset=0.0>
    {0.0} <music21.layout.SystemLayout>
    {0.0} <music21.layout.StaffLayout distance 104.07, staffNumber 1, staffSize None, staffLines None>
    {0.0} <music21.clef.PercussionClef>
    {0.0} <music21.key.KeySignature of no sharps or flats>
    {0.0} <music21.meter.TimeSignature 4/4>
    {0.0} <music21.note.Rest rest>
{4.0} <music21.stream.Measure 2 offset=4.0>
    {0.0} <music21.stream.Voice 1>
        {0.0} <music21.note.Rest rest>
        {1.0} <music21.note.Rest rest>
        {1.5} <music21.note.Rest rest>
        {1.75} <music21.note.Rest rest>
        {1.875} <music21.note.Rest rest>
        {1.9375} <music21.note.Rest rest>
        {1.9688} <music21.note.Note C>
        {2.0} <music21.chord.Chord C4 C4>
        {3.0} <music21.note.Note C>
    {0.0} <music21.stream.Voice 2>
        {0.0} <music21.note.Rest rest>
        {2.0} <music21.note.Rest rest>
        {3.0} <music21.note.Note C>
    ...

I am not sure how many edge cases one can run into for this.

For now, I think catching parts with a PercussionClef object in them and removing them from the score should be a safe preprocessing step.