referred to above can be played not only by the fourth finger on the E-string in first position, but also by the fourth finger in fifth position on the A-string, in ninth position on the D-string, and in thirteenth position on the G-string. Violinists often change positions on the lower strings, sometimes to the consternation of composers and much to the confusion of beginners. This is usually done to handle a musical passage which would otherwise require fast switching (or "crossing") of strings. It is also done to produce a particular timbre: the same note will sound substantially different depending on which string is used to play it. That "high" B, when played on the E-string (the highest, usually a mono-core metal string) can have a clear, even piercing timbre; the same "high" B played on the A-string or D-string or G-string (usually wrapped strings rather than mono-core) may sound "warmer" or less abrasive. For this reason violinists often avoid playing a single note on the E-string within a phrase of notes on the A-string, as one E-string note would stand out with a different timbre. Different strings have different tone qualities, because of their different physical composition and their different resonances on the instrument. The choice of timbres on different strings is vital to the musicality of the instrument, and intermediate and advanced players will often deliberately play in a higher position on a lower string for effect. This effect is sometimes indicated by the composer or arranger. The most common indication uses the letter name of the string: for example, if a composer wants a passage that would otherwise be taken on the D-string to be played on the G-string, they write "sul G" or "G Saite" or "auf G" or "G corde" (or simply, "on G") in the part. Occasionally, numbers or roman numerals are used, so the example might be written "4. corde" or "IV corde" (as above, with the highest string being No. 1 and the lowest No. 4); the simplest way to indicate which string to play is to write the number (e.g., "IV" or "III") alone. Open strings A special timbre results from playing a note without touching its string with a finger, thus sounding the lowest note on that string. Such a note is said to be played on an open string. Open string notes (G, D, A, E) have a very