He sought advice from the leading classical guitarists of the time, notably Andrés Segovia and Narciso Yepes, both of them players of Ramírez six-string guitars.

[4] In Ser Instrumento,[5] Yepes mentions that the reasons that led him to carry out the "design" (diseño),[6] of his instrument were acoustical/physical ("físicas") and musical ("musicales").

[6] After some "initial protest"[3] that the 10-string guitar envisioned by Yepes was "impossible"[7] to construct, Ramírez agreed to the commission and completed the first of these instruments in March 1964.

However, unlike earlier 6- or 10-stringed guitars, the normal tuning of the strings Yepes added "also incorporates all the natural resonance that the instrument lacked in eight of twelve notes of the equal tempered scale".

"[12] Segovia, though, was highly critical of Yepes's innovation, writing in 1974 that, "I absolutely do not believe that the guitar requires additional strings, neither at the right nor at the left of its fingerboard ... the six it traditionally possesses are quite sufficient.