Use MusicXML viewer to view MusicXML files.
You can display MusicXML files from your Android device's Music directory or a secondary directory e.g. Dropbox.

It supports a subset of MusicXML V3.0 including:
- Partwise and timewise formats.
- Compressed MusicXML (mxl).
- Multiple parts (for instruments playing at the same time).
- Multiple clefs per part e.g. piano.
- Multiple voices per clef.
- Clefs: percussion, treble, alto, tenor, base, treble and bass ottava alta and ottava bassa.
- Standard key signatures up to 7 sharps and 7 flats.
- All time signatures up to 99/99.
- Notes and rests from breve (double whole note) to hemi-demi-semi-quaver (64th note).
- Dotted and double-dotted notes and rests.
- Sharps, flats, double sharps, double flats, naturals.
- Grace notes.
- Beams (within bars, not between bars or between clefs).
- Tuplets (triplets, duplets etc.). Nested tuplets are not supported.
- Ties.
- Repeats, segno and coda.
- Breath marks.
- Bow marks.
- Cue notes.
- Clef changes.
- Key signature changes.
- Time signature changes.
- Octave up/down lines.
- Title, composer, copyright.
- Rehearsal marks.
- Articulations: staccato, accent, tenuto, fermata.
- Ornamentations: trills, turns, mordents,

Features:
- View MusicXML files.
- Menu item to display at concert pitch. Note that stem up/stem down is not recalculated.
- Limited play facility, including transposing, changing tempo and lead-in.
- File synchronisation, for example using Dropbox.

MusicXML Viewer integrates with file synchronising apps e.g. Dropbox.
This means you can open files that are in your Dropbox directory, but you still need to use Dropbox to synchronise the files.
Note: on a Nexus7, Dropbox does not download a file to the tablet until you try to open the file from within Dropbox.

Experimental free bonus feature:
- Sight Reader: On some Android devices (Android >= 3.1 and supporting USB On-The-Go) it is possible to plug in a MIDI keyboard. The score then shows you what notes need to be played. When you have played the notes, they turn green and the score moves on to the next chord.
Sight reader is limited to around the first 10 notes of the score. To use sight reader for the full score, you need to use in-app purchasing to buy the ad-free version.
There are some debugging features in the Settings menu to help with any issues in Sight Reader.
I have tested this on a Nexus7 and M-Audio Keystation 61 MIDI keyboard (powered externally from a POWERED USB hub).

This app is supported by advertisements. You can use an in-app purchase to remove the ads.

If you find a problem, please email me at don.dev.acct@gmail.com:
- The MusicXML file.
- A gif file showing the error.
- A description of the problem e.g. "In bar 17 the third note in the treble clef should be shown as a...".