Ken,
There are several components that make the 3000s vocalizer work. First, as Donny stated, you must have a good voice.
Next, you must have good vocal control. This means not raising or lowering your vocal levels by a significant margin while using the vocalizer.
You must also have a high-quality mic, and I'm not talking about the SM58. While the SM58 was a good mic 15 years ago, by today's standards it's marginal at best. I, and a number of other performers, have experienced good to excellent results using the Samson Q7 handheld, and the Crown CM-311A headset mics. The Samson sells for about $200, while there have ben sales on the Q7 for under $100 on some internet sites.
Additionally, the settings are extremely important. Most of the problems relate to the lead to harmony ratio, which should be set at about 30 to 35 percent of the lead. In doing this the harmony component is where it should be--in the background. Using a 50/50 harmony to lead ratio usually results in distortion and overdriving.
The correct type of harmony will depend upon your vocal range. I have a deep, soft voice, therefore HighMaleQua works best for me. Some singers with higher voices will often select MensChoir because it is a bit lower. In this respect, you will have to experiment in order to determine which works best for you--everyone is differrent, but fortunately, there are loads of harmony types to select from.
Hope this helps,
Gary
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Travlin' Easy