An electronic organ uses several top octave synthesizer circuits for producing the various tones used in the organ. Each of the top octave synthesizers is capable of producing any tone which can be produced by the organ. As a consequence, the outputs of each synthesizer are applied to a coupler circuit, which in turn is connected to an octave assignment switching tree for directing the tones coupled to the inputs of the switching tree to individual leads, each corresponding to a different octave in the range of tones produced by the organ. The similar octave leads from each of the different octave switching circuits are connected together to common flute octave buses, so that the filters connected to the output buses have substantially fewer tones appearing at the input than one which would have the full tone range of the organ. Typically, the range of tones appearing at a filter input is one octave or less.