Loop Pedals allow you to record yourself for vocals, guitar, synth and any medium possible. For some devices their is a direct line to the pedal such as guitars where the microphone is already within the guitar but sometimes it is external for vocalists or trombone players. Ether way, what always happens is that it records the frequencys emitted and then will loop it. While you cannot change pitch on pedals you can turn up the amplitude of the sound. Loop pedals are helpful for bands that are small so that they can keep their versatility for songwriting but still have enough harmonic density. However they have to be used tastefully!