Violin where a stopped note sounds a unison or octave with another (open) string, causing it to resonate sympathetically. Students often use these ringing tones to check the intonation of the stopped note by seeing if it is harmonious with the open string. For example, when playing the stopped pitch "A" on the G string, the violinist could play the open D string at the same time, to check the intonation of the stopped "A". If the "A" is in tune, the "A" and the open D string should produce a harmonious perfect fourth. Violins are tuned in perfect fifths, like
Violin Concerto No. 1 (Paganini) orchestra compared to the solo violin, because the orchestral string section plays less frequently on open strings, with the result that the solo violin part emerges more clearly and brightly from the orchestral accompaniment. Contemporary audiences did not realise that Paganini had retuned his instrument, and were thus all the more amazed at what he appeared able to play. (The more musically adept members of the audience would have recognised the distinctive sound of a violin's open string, and would have observed that this fell on the keynote of work (E-flat), and would have therefore realised that Paganini had re-tuned