Complex sentence: This instrument has two melody strings and four drones tuned such that by turning drones on or off, the instrument can be played in multiple keys (e.g., C and G or G and D).
Split into simpler sentences: This instrument has two melody strings and four drones. The drone strings are tuned so that by turning them on or off, the instrument can be played in multiple keys (e.g., C and G or G and D).