Basics

Add your user to the audio group, and install festival-english.

echo "(Parameter.set 'Audio_Method 'Audio_Command)" >> /usr/share/festival/voices.scm

echo "(Parameter.set 'Audio_Command "aplay -q -c 1 -t raw -f s16 -r $SR $FILE")" /usr/share/festival/voices.scm

Set Default Voice

Edit ~/.festivalrc with

(set! voice_default voice_cmu_us_slt_arctic_hts)

Or change the order in /usr/share/festival/voices.scm