The Bender Accessory from Teenage Engineering allows physical control of the oscillation on your OP-1 Portable Synthesizer. Simply mount this accessory onto the orange knob of the synthesizer to control the LFO. It comes with a rubber band, which can be attached to the blue knob for elasticity. Simply select the Bender LFO in the LFO browser to bend any synthesizer parameter, be it pitch or filter.
Note: White encoder sets the amount of LFO, and green and blue encoders control the destination. You can change the bend direction using Shift + orange encoder.