The Beastie Boy’s 1998 record Hello Nasty included their massive hit “Intergalactic”, which won the GRAMMY Award for Best Rap Performance by a Duo or Group in 1999. The robotic vocal hook that opens the song and appears after every verse (“Intergalactic Planetary, Planetary Intergalactic”) is a classic vocoder effect, likely created with a classic hardware vocoder from the 80s or 90s. The vocoder in iZotope’s VocalSynth can also be used to create a vocal effect like this.
With all vocoders, there are two signals that combine to create the effect: the carrier, which is usually a synthesizer, and the modulator, which is usually a voice. In this case, the carrier was likely a straightforward sawtooth wave generated by an analog synth, and the modulator was the spoken vocal track.
The vocoder inside VocalSynth has a preset designed to emulate this carrier sound called “Planet Galaxy.” Insert VocalSynth on the vocal track you want to process (and use as the modulator), and set it for MIDI input in mono mode. Add a little bit of saturation with the Distort module, and some fast slap-back style Delay for the full effect!