 Sometimes string resonance is used in the construction of the instrument, like for instance the Sympathetic strings in many Eastern instruments.According to a 2007 Grove Music Online article on "duplex scaling", Steinway developed a system of Aliquot stringing to provide sympathetic resonance, with the intention of enriching the treble register of the piano.In the "octave duplex" piano by Hoerr of Toronto, each note had four strings, of which two, three or four could be struck by the hammer depending on the depression of any of four pedals.