If you're working with recorded vocals, a software package might work. But, as noted above, it takes lots of learning, experience and time.
If you're looking for live vocal harmonies, Dan, above, is right. The TC products are probably the best there is. I've used them for years and found nothing better, just pull up one of the hundreds of programs and instant harmony! Doubling, two part, three part, full choirs, reverbs, delays; the TC units, at least for me, can do it all.

Jeff


Win11, Intel i7 7700K 4.2Ghz, 32Gb RAM, 2x1Tb HD, 500Gb NVMe, BIAB/RB 2024, MOTU 828MK3 audio, MOTU Midi Express, Yamaha Montage 7, DX7II, TX802, Motif XS Rack, Roland Fantom XR Rack, Oberheim Matrix 1000, VoiceLive3 Extreme, Kontakt 6, SampleTank 4.3