Had to go with Roger Troutman on this topic,
Roger is a key player in pushing the whole Funk movement to the world, armed with a costumed made Electro Harmonix “Golden Throat” talkbox and a Yamaha DX100 FM Synthesizer he pioneered a style that is still current to this very day, His talkbox singing is not to be confused with a vocoder or the nowadays auto-tune effect. Roger was a late comer into the band Parliament-Funkadelic and the first band he played in was The Crusaders. In 1979 George Clinton signed Roger and his brothers to his label Uncle Jam Records and this was the birth of the mighty band called Zapp, a year later Zapp were signed to Warner Brothers Records and released their self titled album which contained the Bootsy Collins produced and Troutman composed smash hit “More Bounce to the Ounce” this particular song has been sampled some 350+ times, it is a big hit for rap producers and rappers in the genres of G-Funk and Gangsta Rap and Rap music in general. Four Zapp albums went onto be gold selling albums.
Roger mastered the art of singing the whole alphabet clearly through the talkbox tube with the added risks of electrocution and sickness while at the same time playing keys and making use of pitch bending and modulation on the Yamaha DX100 as well as a Minimoog. The particular patch he used on the synthesizer was tweaked a little to add to the desired effect. Roger often layered his talkbox vocals with some cool panning too to add even more genius to his sound. I think an FM Pulse or FM Sawtooth tweaked patch can help give the effect but you also have to have the correct horn driver and amplifier to capture this sound as best as possible. Zapp and Roger used great FM Synthesis techniques also in their re-creation of synth instruments used in their recordings, I also read somewhere that they may have used some type of LINN Drum machine to get that heavy slammin’ snare sound which frequently got overlayed with real handclaps.
Here is a link to some Roger Troutman magic,
Synthzone.com, (2016). Yamaha DX 100 and Roger Troutman – Synth Zone Forums. [online] Available at: http://www.synthzone.com/forum/ubbthreads.php/topics/71719/3 [Accessed 29 Feb. 2016].
Wikipedia, (2016). Roger Troutman. [online] Available at: https://en.wikipedia.org/wiki/Roger_Troutman [Accessed 29 Feb. 2016].
YouTube, (2016). Roger Troutman Part 1. [online] Available at: http://www.youtube.com/watch?v=DGUH0C09l70 [Accessed 29 Feb. 2016].
YouTube, (2016). Vontel & Roger Troutman – Say Playa. [online] Available at: https://youtu.be/yfsiyf6Pk8E [Accessed 29 Feb. 2016].