Vocalizer Pro is described as 'powerful vocoder effect plugin for Mac and Windows available in a variety of formats including the popular VST and Audio Unit formats' and is an app in the Audio & Music category. There are four alternatives to Vocalizer Pro for Windows, Mac, FL Studio, iPad and iPhone. The best alternative is Vocodex. It's not free, so if you're looking for a free alternative, you could try TAL-Vocoder or mda Talkbox.
Vocodex is a stunning, high quality vocoder available in VST and native FL Studio plugin formats. FEATURES Speech enhancement contouring of noise or modulator pass-through. Modulator noise reduction to reduce ambient noise bleeding through carrier.
TAL-Vocoder is a VST/AU plugin that emulates the sound of vintage vocoders from the early 80s. It provides 11 bands and users analog modeled components in combination with digital algorithms such as the SFFT (Short-Time Fast Fourier Transform).