Not on the OST. Is there .strm file or .wav recording of this somewhere.

You can easily rip it yourself through PSXMC (grab an image of the game somewhere, burn it, and have the software analyse it). If memory serves me right, the instrumental version of Add'ua you seek is on a single "file" also containing the short music you hear when the main menu loads up. You'll need to do some editing/cutting.

Or I would recommend jPSXdec (https://kenai.com/projects/jpsxdec/pages/Home). Same procedure = scan ISO, convert tracks to WAV.