Currently , the most common tuning fork sounds the note of A = 440 Hz , because this is the standard concert pitch , which is used as tuning note by some orchestras , it being the pitch of the violin 's second string , the first string of the viola , and an octave above the first string of the cello , all played open .
It is the pitch of the violin 's second string , the first string of the viola , and an octave above the first string of the cello , all played open .