Tuning signature modes in guitars—A lesson by Faustino Conde

The low-frequency range strongly determines sound quality in a classical Spanish guitar. In the range above the fundamental air mode A0 at roughly 100 Hz and below 400 Hz, most guitars reveal one or two main plate/body resonances. A progressive construction from Faustino Conde in 1964 was meant to leverage versatility across classical and flamenco guitar styles, and it reveals four distinct and well-balanced resonances in the mentioned range. Related modes have intensely been discussed for the violin, the so-called signature modes, but not necessarily for the guitar. This contribution points at constructive reasons behind the multiple resonances, identifies related tuning parameters which are finally part of a general analytical model. Analytical results deliver related eigenfrequencies while numerical analyses yield the modes’ relative mobility, in agreement with both, an experimental set-up and diverse measurements at the guitar. In conclusion, all guitars could have more than two resonances, but the parametrical space of the four related parameters is wide and the tuning is delicate.