In 1964, Yepes performed the "Concierto de Aranjuez" with the Berlin Philharmonic Orchestra, premièring the ten-string guitar, which he invented in collaboration with the renowned guitar maker José Ramírez III. The instrument made it possible to transcribe works originally written for baroque lute without deleterious transposition of the bass notes. However, the main reason for the invention of this instrument was the addition of string resonators tuned to C, A#, G#, F#, which resulted in the first guitar with truly chromatic string resonance – similar to that of the piano with its sustain/pedal mechanism.