To a degree. Deathspeak would allow you to understand, communicate with and compel ANY undead (vampires, ghosts, ghouls, zombies, etc.; even LICHES) to do your bidding, transcending any mental barriers and language barriers...
“…Judge not what a man has done, but judge what he could have done if he was a different bloke altogether. For art thou a leper? And a leper can changeth his spots…” --Rudy Wade, Misfits (Series 4, Episode 8)