Long ago I owned the KORG ih vocal harmonizer and, because I cannot sing at all so this thing sounded terrible with my voice singing.

BUT as soon as Wietse (singer of the 'band') startet using his voice........ the ih sounded superb

The Ketron SD1's vocal harmonizer did not blow me away, not even with Wietses voice, because of:
a. The mono-output
b. The harmony voices poor quality

Therefore I purchased the TC Helicon VoiceWorks that is realy amazing...but the singers input voice/skills are very important !! The TC's price is about 1/3 of the Tyros' price !

So, please don't expect a perfect sounding harmony from a machine that is not specially designed for the job. (e.g a keyboard)
OR
Singer who is not fully trained, or hasn't the skills to USE a Vocal Harmonizer.

When 'garbage' comes in......'garbage multiplied by 4' comes out
Don't blame the electronics/software for this!

Please realize the demo is produced in only a few minutes time and the musician did not take the time to tune all levels afterwards.