Boss VE-2 Harmonizer from Sweetwater listed new at $275. Perfect for single players or groups. Adds harmonies by combining input from the guitar and mic. It's a tool common to lots of one person acts I've seen. I bought this to just fool around with. Never gigged. Never left my music room. In the original box. I'm in Green Valley and can meet at a neutral halfway public spot.
• An easy way to create real-time vocal harmonies
• Plug and play simplicity
• Create harmonies by manually setting the song key or by connecting your guitar via the Auto Harmony function
• Hybrid mode creates harmonies based on both chords you play and the manual key setting
• Choose from 24 one- and two-voice harmony types
• Easily dial up reverb, delay, and combination reverb + delay effects with a single knob
• Lets you apply subtle pitch correction as you sing
• Three memory slots let you store and quickly recall your favorite settings
• XLR mic input with phantom power that's available even when running on batteries
• USB audio function lets you capture processed vocal sounds into your computer
• Runs on 4 x AA batteries or AC adapter