scordatura explained
The technique of deliberately mistuning one or more strings of a stringed instrument to achieve unusual sonorities or facilitate difficult passages
In Depth
Scordatura was common in Baroque music, where violinists, lutenists, and viol players regularly retuned to access different keys, double-stop combinations, and tonal colours. Biber's Mystery Sonatas use a different scordatura for almost every movement, creating fifteen distinct timbral worlds. In modern music, composers use scordatura for microtonal effects and to extend the instrument's range. Guitarists frequently use drop-D tuning, the most common surviving scordatura in popular music.
Biber's Mystery Sonata No. 11 requires the violinist to cross the two middle strings, creating a tuning that allows chords physically impossible in standard tuning.