[orca-list] alternative synthesizers with Orca?

[Ryan Mann <rmann samobile net>]

Hello.  I am running Ubuntu 14.04 on an Intel iMac from 2006.  I would
like to run an alternative synthesizer such as Festival with Orca. I
have installed Festival and the US voices for Festival.  I start Orca
Preferences by hitting modifier+space.  On the Voices tab, there is a
combo box to select the synthesizer that I want to use.  Festival isn't
one of the synthesizers listed.  I went into Orca help by pressing
Modifier+1 and hitting F1 to open the documentation.  I didn't find
anything about using alternative synthesizers with Orca.  What do I need
to do to run Festival with Orca?
Thanks.