Koszalin is a full stereo frequency shifter (2 ins / 4 outs) offering both quasi-exponential and linear frequency change of up to +/-5kHz as well as full stereo feedback under voltage control. Frequency shifting results in linear translation of signal spectrum producing all kinds of atonal sounds. It should not be confused with frequency scaling, also known as pitch shifting. Complex phase cancellation patterns occurring with frequency shifting and deep feedback produce spectacular barber-pole effects. Koszalin offers direct control of feedback amount, feedback routing, and feedback response. It also facilitates frequency modulation of any stereo audio signal, thanks to the linear TZFM input.