Spectral analysis of several American Idol contestants' voices showed me that those which sound good to me also feature a strong second harmonic. It's well known that tube guitar amplifiers are preferred for their second-harmonic distortion when overdriven (as guitar amplifiers often are). Thus, can we artificially boost the second-harmonic content of a singer's voice? This project attempts to do so by a straightforward method. Below shows a portion of one of the 12 hierarchy boards in the project -- one for each note in an octave of piano keys.
The project measures the ratio of each frequency channel's level to the composite level. Anything detected boosts the level of the next channel at twice the frequency. The ratios are taken with the -1452's log and antilog blocks to save instructions.
Playing a podcast through this project, it tends to increase vocal "presence" when the effect level is set moderately. At an extreme setting a podcast voice transforms into something like that of an over-processed FM radio announcer. The project is attached in case anyone might wish to try it.