These guitar basses are a reproduction of what was made between the end of the 19th century and the first half of the 20th century, but with a lower tension compared to what was used at that time, because this type of strings are designed to be installed in original instruments. If the original historical working voltages are required, the Seta 900 basses are the best. These underpants have a real silk lining. Silk is a natural product that cannot be uniform in gauge, so it can happen that bass strings at the 12th fret can be flat or moderately sharp. Ideally, 435 Hz should be used as a reference. Finally, it is recommended, when not playing strings, to tune the wired basses a semitone lower for longer life.