Prim strings for electric violins requiring non-standard tuning. F tuning, Bb tuning, and Bb XL (extra length). Chromesteel core. Sold individually.  Strings should generally be changed every 6–12 months, though students usually change them less frequently. Even if strings haven't broken, they gradually lose their brilliance and responsiveness — if your instrument sounds dull or takes longer to settle in tune, it's time for a fresh set.