How does meshuggah pulloff their solos?

I just recently got into meshuggah and now think they are the greatest and most original band ever made. Anyways, how do they make those crazy/weird solos work with the equally as complicated riff? Even though both the riff and the solos are weird, they seem to fit really well. Does anyone know what kind of scales or techniques if any that they use for their solos because it's got a totally original sound from anything i've ever heard.