How the Sheet Music to Guitar Tab Converter works

Tablature is a different way of writing the same pitches. The tool reads each note's pitch from the MusicXML file, finds the strings and frets that produce exactly that pitch, and picks one:

What is checked after every conversion, and what is not

Two checks run each time, and the two lines under the tab report them.

• Every printed number. The sum above is worked out again for each fret the tool printed and compared with the sounding pitch the tool read for that note. If any differs, the tab is withheld.
• Every note in the file. The file is read a second time by a much simpler routine that shares no code with the first. It only counts the notes that have a pitch and looks at their staff, whether they are cue notes and whether they are chord notes. The counts must add up, and the written pitches of the converted notes must be the same in both readings, in the same order:

If they do not add up, the tool says "Note count does not reconcile" instead of "Every note placed". When notes were left out on purpose (other staves, cue notes) the verdict says how many rather than reporting a clean pass. Those notes are counted; they are not listed one by one.

Not double-checked: the transposition is applied by the main reading only, and note timing is used for spacing and ties but is not re-derived by the second count. The second count is a plain scan of the text. Unusual but legal XML, such as a closing tag spelled inside an attribute value or a part nested inside another element, can make it disagree with a correct tab; the tool then reports that the count does not reconcile.

An XML entity can stand for whole notes, and neither reading expands one. So a file is refused with a message if its document type declaration declares an entity, whether or not the file goes on to use it, and if it uses any entity reference other than the five standard ones (& < > " ') and numbered characters such as é, wherever in the file it stands. That includes a named character like é, which the MusicXML document type would allow; write the letter itself.

Notes that do not fit

The lowest note in standard tuning is the open low E string (E2). The highest is whatever fret you allow on the high e string: fret 15 by default, up to 24. A note below or above that range is marked with an asterisk above the staff and listed with its measure number. It is never moved to a nearby note. The same goes for two notes that sound together but exist only on the same string, a chord that would need a stretch of more than 4 frets, a chord of more than six notes, and quarter-tones.

Which octave

Guitar music is written one octave above where it sounds. MusicXML files record that in one of two ways, and the tool takes each file at its word.

• Some files store the written pitch and add a <transpose> element with an octave change of −1. The guitar staff in the MusicXML specification's own tablature example is written this way. The tool applies it:

• Other files store the sounding pitch and show the octave with an octave clef and no <transpose>. A guitar part exported by MuseScore 3 that we examined is written this way. The tool uses the stored pitch as it is and does not lower it a second time; it mentions the octave clef under the tab.

A piano or vocal part has neither marking, so its notes are placed at the pitch written. That can come out an octave higher on the neck than a guitarist reading the same staff would play it. The octave setting moves the whole piece by exactly twelve semitones either way, and the tab says when it has done so. On Auto, the piece stays where the file puts it if every note fits; otherwise the tool counts the unplayable notes at each of the three octaves and keeps the lowest count, telling you the numbers.

Tied notes

A note marked as the end of a tie is left unprinted only when its string is still sounding that note. All of this must hold: a note of the same pitch that starts a tie, and is not a grace note, ends at exactly the moment this one begins; that note was placed; the tied note belongs on the same string and fret; and nothing else is struck on that string from then until the tied note begins, including in the tied note's own column. "Until" follows playing order, not the clock, so a grace note or another chord note that shares the moment still counts.

In every other case the note is struck and printed, and the tool says why, with measure numbers, under the tab and in the copied or downloaded text. The reasons are kept apart: the string was needed for another note; the fingering placed the note on a different string; the note it is tied from could not be placed; it is tied from a grace note, which is never held; or the tie mark connects to nothing, as with a tie that is never finished in the file, one separated from its end by a rest, or one that another note has already ended. A struck tie sounds the right pitch at the right moment; it adds one attack that the score does not have. The check that runs after every conversion walks the finished tab string by string in playing order and fails if a hidden note's string is sounding anything else.

Choosing between correct positions

Most pitches can be played in several places. The choice among them is a judgement about comfort, not a fact from a source, and it never changes a pitch. The tool looks for the fingering with the least hand movement over the whole piece, with a mild preference for low frets and open strings:

The minimum is found exactly, by dynamic programming over the hand position at each step. It does not know about slides, bends, hammer-ons, which finger to use, or whether a long note in one voice can keep ringing while another voice moves. Treat the fingering as a starting point.

What is read from the file

• Partwise MusicXML (score-partwise), uncompressed or compressed (.mxl).
• Pitch: step, alteration and octave, including double sharps and double flats.
• Transposition: chromatic and octave-change.
• Rhythm: divisions and durations, used to space the columns in proportion to time. Both must be whole numbers (see below).
• Chords, several voices in one measure (backup and forward), rests and grace notes.
• Ties, as described above.
• Notes the file marks as not printed (print-object="no") are converted like any other note. The specification says of that attribute only that it "specifies whether or not to print an object"; unlike a cue note, nothing makes such a note silent. The tool says how many of the notes it read carry the mark, under the tab and in the copied or downloaded text, since the printed score may not show them.

What is skipped, and said so

• Timewise files (score-timewise) are refused with a message.
• A part whose top staff has a tablature or percussion clef anywhere in it is skipped as a whole.
• A part the tool cannot read reliably (an unreadable pitch or duration, a transposition with no value) is skipped with the reason. The other parts of the file stay available.
• Only notes on the top staff are converted. Notes marked for any other staff, as in a piano part, are counted and reported in the verdict and under the tab, whether or not the part declares more than one staff.
• A part with a fractional duration (<duration>0.5</duration>) is skipped with that reason. The format allows decimals but prefers whole numbers, "to avoid roundoff errors" in the specification's words, and this tool decides which notes start together and whether a tie meets its end by adding durations up, which is exact only for whole numbers. Exporting the score again normally gives whole numbers.
• A part is also skipped, with the reason, when a note is marked as a chord tone but no note comes before it in its measure, when a chord mixes a grace note with an ordinary note, or when its durations add up to more than 9,007,199,254,740,991 units.
• Cue notes and unpitched notes are skipped and counted.
• A forward or backup of zero length, which some programs write, is read as no movement.
• Repeats and endings are not written out: each measure appears once, in written order.
• Alternate tunings, bass, ukulele, playback and Guitar Pro export are not offered.
• Limits: a file over 20 MB, a compressed file that unpacks to more than 32 MB, or a part with more than 100,000 notes is refused with a message.

What the page address keeps

The address keeps your settings (capo, highest fret, octave, measures per line), so a bookmark brings them back. It never contains the file. That is why there is no "copy link to this result" button here: a link cannot rebuild a tab without the file, which stays on your device.

This tool cannot be published unless it reproduces every example below. 10 are copied from a published source. 24 were worked by hand from the cited rule.