The Khokarsan language employed a syllabic script similar to that used by the ancient Maya of Mesoamerica. The complete Khokarsan syllabary and diagram of glyphs can be found here. A detailed article by Philip José Farmer on the Khokarsan language can be found in the addenda to the limited edition of Gods of Opar: Tales of Lost Khokarsa (but does not appear in the trade edition of that book).
In the following brief audio clips, Philip José Farmer demonstrates the pronunciation of “Hadon of Opar,” the protagonist of Hadon of Ancient Opar (1974), Flight to Opar (1976), and Hadon, King of Opar (forthcoming 2015). These recordings are from the Edgar Rice Burroughs Dum-Dum convention held on September 1, 1973 in Toronto, Ontario, Canada.
h: voiceless glottal fricative (expressed somewhat more strongly than in English h)
a: low central spread vowel (as in Spanish)
d: voiced dental stop
o: mid-back rounded vowel (as in Spanish)
n: voiced dental nasal