Demi-filées are metal-wound strings on a natural gut or silk core, with the characteristic that the winding is not tight, but spaced by the diameter of the wire itself, so that the string is essentially wound in half, hence the name in French. In reality, in the examples of demi-filée that have come down to us, the winding is much more spaced.

The sound is intermediate between that of a bare gut string and a wound one, and is therefore particularly suitable for the middle register of the Baroque violin (D), Viola da gamba family and Three-order harp, as a timbre transition string. Or it is also historically attested for the basses of the Lute, archlute,  or theorbo.

Its invention, however, could have derived, as Mimmo Peruffo claims, not from a timbre requirement, but from the inability to draw the metal beyond a certain limit, which made it impossible to make a tightly wound string, unless very thin cores were used, which were therefore extremely fragile (in addition to the fact that the timbre would become strongly metallic).

It should also be noted that this is a very delicate string, and the metal coils tend to bunch up near the bridge and nut when tuning, with the risk of making the string sound false. Its use is therefore recommended only in cases of absolute necessity.

For example, the D of the demi-filée violin was used only by French violinists in the 19th century, but this is explained by the fact that the Parisian pitch was very low, and therefore the D in bare gut would have been extremely thick and therefore dull. For the standard baroque pitch of 415, however, a demi-filée is not at all necessary, and our Cordoncino di Roma is not only sufficient, but actually has a much richer and more powerful sound.

Due to the defects that we found in the demi-filée, even though we are able to make them in a historical manner, we were able to obtain the same effect with the wire incorporated into the gut string. This completely eliminates the problems described above, and the string is of a smaller diameter than that of bare gut, with a beautiful sound even if slightly dark.

For the moment we propose demi-filées for the D of the violin and for the C of the low viola da gamba.