French Tablature Made Reasonably Easy

The system used for reading lyra viol literature employs a six-line staff representing the strings of the instrument with the thinnest, highest pitched string appearing at the top.

The letters of the alphabet are used to represent, not musical pitches, but the numbered frets going "up" (down in real terms) the neck of the viol.  In the example above from an instructional preface by John Playford, the highest pitches shown going to the right are on played on the "h" or seventh fret, a fifth above the nut or where open strings are shown by  letter "a."
Tuning the Instrument

The idea of showing intervals using these letter symbols is used widely as a means of providing instructions for tuning the instrument. The example below shows that if one stops the second string on the third fret and checks it against the open top string, "harp-way sharp" tuing would yield a unison.  Since the "d" fret is three half steps away from the open or "a" fret (actually the nut) the two adjacent open strings sound the interval of a minor third.  Thus the "e" interval shown next is a major third, the "f" is a fourth, "h" a fifth and the "f" another fourth.
Rhythms are indicated utilizing symbols similar to those still in use.

Although this system of notation is widely referred to as "french tablature" the viola da gamba literature relying upon it is mostly British.  One notable exception is the collection of solo suites by Le Sieur de Machy, printed in Paris in 1685.  Written for an instrument with seven strings, the bottom string is shown below the staff, a practice that is sometimes followed with British music for a six string viol on a five line staff.  De Machy's "suittes" are more typical of French music of this period rather than the usual music one encounters in tablature form, and might have been almost as easily written out in ordinary musical notation.  It is rather telling, however, that this extremely chordal, contrapuntal music seems more easily read in tablature form, and as a matter of fact , de Machy himself recommended starting beginners off in tablature.