im doing a final project about making a guitar pedal effect, and my lecturer ask me to compare it to commercial guitar pedal using an oscilloscope. i made 4 effect, reverb, echo, chorus, overdrive, all of this effect showing almost same result as the commercial effects, but the reverb one doesnt do well. can anyone tell me a theory that can answer this kind of wave

 

The harmonics present in the final waveform is the result of phase modulating a waveform with a reverb waveform. The harmonics present will depend on the amount of phase shift that is caused by the length and shape of the reverb waveform. The two examples displayed probably have different reverb cycle times and waveshapes resulting in one case, a predominance of even harmonics and odd harmonics in the other.