invert a momentary switch with a relay
Here's the relay schematic. 



The coil (terminals 85 &amp; 86) is to be energised by your foot pedal switch.

The NC contact (terminals 30 &amp; 87a) is what you need to invert the foot pedal switch function.

When the coil is energised, the NC contact (terminals 30 &amp; 87a) opens and the NO contact (terminals 30 &amp; 87) closes.