Adrian Le Roy (1520 - 1598) composed for both the lute and guitar.  Le Roy was also a music publisher, along with Robert Ballard, in Paris.  Le Roy and Ballard were the Royal music printers for Kings Henri II, Charles IX, Henri III and Henri IV.  4 books of Le Roy's guitar music were printed in the 1550s, including his Cinqiesme Livre de Guiterre... in 1554.  Cinqiesme Livre is the fifth and final book (that we know of) published in a series of guitar books by Le Roy and Ballard in Paris in the 1550s.  The series includes 4 guitar books by Le Roy, and Brayssing's guitar book which is discussed here.   Cinqiesme Livre is a book of songs/chansons set to 4-course guitar music by Le Roy.  The songs in the book are by a variety of composers, indicated in the contents page below.  The song melodies and lyrics are included in Cinqiesme Livre as late Period mensural notation.  The guitar accompaniments in the book are written in French Tablature.

Contents of Adrian Le Roy's Cinqiesme Livre from 1554

I'ay tant bon credit qu'on voudra is a song by Jaques Arcadet (c. 1504 - 1568).  The guitar accompaniment and arrangement is by Adrian Le Roy.  The notation used in Cinqiesme Livre is somewhat tricky, in that the repetition markings used in the mensural notation are not included with the guitar accompaniment.  This can be problematic when trying to interpret and arrange the music.  When working with this book, one has to consider the mensural notation to ensure that the guitar transcription is accurate in structure.  I'ay tant bon credit is a good example:  

Facsimile of Adrian Le Roy's arrangement of I'ay tant bon credit from Cinqiesme Livre (1554).  Lyrics and mensural notation on the left page, with the guitar part (french tablature) on the right.  

In the mensural notation, the first repeat symbol [ :||: - also called a signum reinceptionis ] is obvious to the modern musician.  The guitar accompaniment ignores this first repeat in the mensural notation, and Le Roy provides a through-composed accompaniment for the first 17 measures of the piece.  The vertical line at the beginning of the 7th measure in the mensural notation indicates that this particular measure is to be skipped on the repeat (you have to count the beats to find the "measure," as no bar lines are provided in mensural notation - fortunately, Le Roy gives us bar lines for the guitar accompaniment!).  The following symbol is used in Cinqiesme Livre to indicate the beginning and ending of a repeated section on the mensural notation:

Of particular interest in the case of I'ay tant bon credit is that this symbol (called a signum congruentiae, but we'll call it a "repeat mark" here, for ease of use, and since that is its primary function in this piece - thats not always the case with the signum congruentia) is only included in the mensural notation, but it is actually used to indicate where the french tablature guitar part repeat begins and ends (although, the first "repeat mark" also doubles to serve as an indicator of where the repeat of the second part of the song lyric/mensural notation begins as well).  For the guitar accompaniment, the section between the two "repeat marks" is repeated, then the guitar part skips to the final 10 measures of the piece.  This is effectively equivalent to a dal segno al coda construct in modern notation (repeat back to the dal segno, until told to play the coda/ending, Da Coda), with the 1st "repeat mark" acting as the dal segno and the second "repeat mark" acting as a "Da Coda" indicator.  All of this notation described so far, is contained on the mensural notation, even though it provides indications to the guitarist!  The only indicator in the guitar accompaniment (right page of the above facsimile) is the following symbol underneath the  18th measure:

This symbol is equivalent to the first "repeat mark" (signum congruentiae) in the mensural notation.  There is no equivalent to a modern "Da Coda" marking in the guitar accompaniment to inform the guitarist of where the "coda" begins.  So, to work this out, the mensural notation has to be paired with the guitar notation.  This works just fine for my purposes, as my goal in transcribing this piece was to prepare a piece for performance with vocals or with a separate instrument (recorder) taking the song's melody line.  Based on the repetition symbols included for this piece, the Period guitarist would likely have needed to experiment with the piece to play the accompaniment properly.  It is possible that a second mark to indicate "Da Coda" was unintentionally omitted by the publisher, but if that is the case, then from my review of the entire book, the publisher made this same mistake at every given opportunity!  The use of the repeat marks above allowed the publisher to print the piece with fewer characters required, thus saving costs on printing.  See below for my transcription of the piece to modern notation, and pairing the vocal and guitar parts together in a single score.  In the transcriptions (with paired guitar and vocal parts) I have used the dal segno al coda (D.S. al Coda) construct, which matches the intent of the original publication (though the modern symbols are used) and confusion between the two parts is eliminated, as they are paired together in the score.  The decision by the original publishers in 1555 to print the mensural notation and guitar parts on separate pages was likely driven by cost and convenience - 1) for convenience of the musicians:  a guitarist and vocalist could stand side by side and perform from the same book, each reading their own part, and 2) to reduce publishing costs:  the mensural notation and guitar tablature are printed separately, rather than 2 pages with both parts printed on each page.

Transcription of I'ay tant bon credit from Adrian Le Roy's Cinqiesme Livre (1554).  Transcribed to modern staff notation and tablature by Johann von Solothurn.

Note that I have made two corrections to the guitar tablature (marked as *1 in the 1st and 9th measures).  In both cases, the top note in the original guitar tablature was D#, which created an obviously unintended dissonance with the D natural in the vocal part.  The original mensural notation was written in the key of F (1 flat).  The guitar part works out to a key of A (3 sharps) with a modern guitar tuning.  It is widely believed that the renaissance guitar would have been tuned such that the open first string would have been a'.  If so, then the tablature in period tuning would have produced a guitar part in the key of D (2 sharps).  It is possible that Le Roy may have intended a higher pitch for his guitar music, but the most likely explanation for the (apparent) difference in key signatures between the guitar accompaniment and mensural notation is simply printing costs.  Note in the facsimile above that the lowest note in the mensural notation is an "E" - if the mensural notation had been printed in a lower key (to match the guitar accompaniment) then ledger lines below the staff would have been required.  Ledger lines would have added cost to publication.  Printed music in period commonly avoids ledger lines, where possible, presumably because of printing costs.  In the transcription above, I have transposed the vocal part to match the key of the guitar.  

See below for transcriptions of the original voice part in its original key, and an arrangement of the piece, transposed for C instruments to perform the melody line.  In the C-instruments arrangement, the guitar part is not modified from Le Roy's tablature (other than correcting the printing error mentioned above), but requires a capo to match the transposed melody line).

Staff notation and modern guitar tablature for I'ay tant bon credit from Cinqiesme Livre (Adrian Le Roy, 1554).  Transcribed by Johann von Solothurn and transposed for C instruments.  To play the guitar part in the key of C, capo to the 3rd fret.