Beginner looking to mod a Billy Bass?

[fluxedo]

I'd like to consider myself someone who is extremely proficient at soldering but never knew the electronics behind it. I tend to do consoles handhelds and frequent those forums associated with those types of project like Modretro. Anyways my dad recently asked if I could help him create a modified Billy Bass for a co worker that could read a music file and have the mouth move accordingly to the song. The setup we have behind it is an MP3 player built inside with it properly mounted on the back of the Billy Bass. This MP3 player will play custom tracks I've created with the vocals of the song on the "left" output and the music on the "right" output. ( I say left and right loosely because this is only to split the audio to then coordinate them to the proper movements on Billy). I'm wanting to have the vocals coordinate with the mouth, the tail move with the music. My question is what circuit or part could I use that could read the audio line and allow the five volts needed for the motor to pass through when the audio is at a certain volume? I've seen people do this with LEDs to create an LED that turns on to the intensity of the music using a TIP31 transistor but I don't know enough about that actual electronics side of electronics to know. I'm also wondering where can I learn electronics online so that next time I could build what I need myself? I've been trying to learn circuit building and understanding electronics but I'm not sure where to start.

 

[(*steve*)]

I believe there is information on the net about someone who converted something like this to speak twitter messages or the like

There may be some useful tips there.

Here is a reference to the hack. I'm sure I saw more detailed information some time long ago when I was vaguely interested.

 

[(*steve*)]

Google "microcontroller speaking fish" for more useful links including this one.