The phrase "middle pedal" refers to a pedal in a piano that is located between the other two pedals. It is used to create special sound effects while playing the piano. Full definition
The large Brembo brakes inspire confidence, too, responding progressively to stabs at the firm middle pedal. (automobilemag.com)
Choose from the middle pedal, left or right, or the levers over either rear wheel. (stroller-envy.com)
My contorted foot has hit fresh air where it anticipated a middle pedal and now my generous braking distance is shrinking as quickly as my panic is rising. (evo.co.uk)