Open G tuning d g b d'>2. </score> is used by the Russian guitar, which has seven strings tuned mostly in triads, in contrast to other guitars, which are tuned mostly in fourths. Dobros use a full six-string tuning with a bottom G: G-B-D-G-B-D, low to high. The two lowest strings are, accordingly, tuned three semitones higher for the lowest string (from E up to G) and two semitones higher for the second-lowest string (from A up to B) while the highest string is tuned two semitones lower (from E down to D), relative to standard tuning. The 5-String Banjo's standard tuning is
Concert pitch D-flat), and are often tuned to match B brass instruments when the two are required to play together. The Stuttgart Conference of 1834 recommended C264 (A440) as the standard pitch based on Scheibler's studies with his Tonometer. For this reason A440 has been referred to as Stuttgart pitch or Scheibler pitch. In 1939, an international conference recommended that the A above middle C be tuned to 440 Hz, now known as "concert pitch". As a technical standard this was taken up by the International Organization for Standardization in 1955 and reaffirmed by them in 1975 as ISO 16. The difference