Traditions entangled with strings
The charango, as most Andean musical instruments, is wrapped in traditions. Perhaps one of the best known is that of the Sereno, Sirinu or Sirena, a kind of Andean "spirit of the music" that lives in springs, streams and ravines. According to tradition, the Sereno tunes instruments and whispers melodies on Tuesdays and Fridays, between midnight and dawn. Only good musicians can hear the Sereno's voice (which comes to their ears alongside the sound of the running water and the whistling wind) and learn the songs to play on the charango and the verses that make up the tonadas.
It is said that the charangos that have been "templados" (tuned), "enserenados", or "encantados" (enchanted) by the Sereno are able to play alone. For this reason their owners have to loosen their strings every night for the instrument to go to sleep, otherwise the charango will always be sounding and, therefore, will end with a terrible sound.
Besides entrusting their charangos to the Sereno, the musicians of the villages located in the Quechua-speaking region of Bolivia (northern Potosí department, Chuquisaca and Cochabamba) usually place the tail of a rattle snake within the body of the instrument after it has been properly ch'allada (blessed). It is said that when these charangos sing, they corner their rivals and enchant the women; their voice is charming and they are the "owners of all tunings" (that is, they can play equally good in any tuning they want). This tradition is not very well looked upon by some charango players who see something "diabolic" in the tail of the rattle snake, perhaps influenced by Christian beliefs and values.
When the charango is made out of a kirkincho shell (quirquincho or armadillo), some musicians sprinkle a bit of ground chili pepper within its body; it is believe that by doing so they will prevent the instrument from cracking. Finally, if the shell belonged to a female animal, the charango players will try to keep the instrument away from the hands of any woman; were they not to do so, the instrument would be "jealous" of her, go out of tune and it would be very difficult to tune it again.
Article. "Serenos de verso, susurros de medianoche", by Juan Mallqui [es].