just add a line to ttsclock script such as

cat /drive0/var/tts/start.pcm | /drive0/var/pcmplay

where start.pcm is the audio file you want to play after the time starts. you do it more elegantly, I'll post the one that selects a random audio file later today. I added as an atttachment to this post the one i use that I like a lot as an example.