There are two basic foot switches used with musical devices.  Latch (latching) switches and momentary switches.  Latching switches "latch" open and closed and are commonly used with guitar amplifiers to activate distortion or other effects.  Momentary switches are either always ON or always OFF, when depressed the signal is interrupted(always ON) or enabled(always OFF.)  Momentary switches are used for sustain pedals (keyboards/synths) and to trigger devices like drum machines, and recording equipment.  I wanted to incorporated both switch types into a single pedal to reduce the number of cables around my jam space, by using the toggle switch on the side I can use either the latch switch or the momentary switch depending on what is required.  Retail momentary foot switches cost around $16, latch foot switches start near $20. The cost to make this pedal was about $5.
Materials:
one plastic travel soap dish
one ¼” mono patch cord (I used a patch cord that could easily be split into two wires)
one 3 pole toggle switch
one latch switch
one momentary switch (these come as either always ON or always OFF. consult your equipment manuals to see which type of momentary switch should be used with your device)
two small machine screws
four self adhesive rubber pads
Tools:
knife or wire stripper
small hand saw
hand drill
drill bits
needle nose pliers
wire cutters
Screw driver
Optional:
Soldering Iron
Solder

Possible Modification:
Two momentary switches. One always On and the other always OFF. This removes the usefulness of the pedal as an amplifier switch but lets you use the pedal with more synth and recording devices.