Yes. Above a compared voltage, the output logic level switches.
Use that to control if an LED will light or not.
All segments off unless the comparator says "let there be light".
It's likely that you will have to play with de-glich stuff or time constants though.
Probably follow the trigger with a timer (555).
Switching at an audio rate is too fast.
http://hyperphysics.phy-astr.gsu.edu...opampvar8.html
Here is info on 7 segment drivers. You can enable or un-enable all segments.
http://www.play-hookey.com/digital/e...eg_driver.html
It might help you decide on an approch or the parent page may give you other ideas.
I'd like to know how you follow up on the project!
Oh yeah, you could use small clip leads to the soundcard or a double jack.
A tee jack (one input two output) connected to the line output on the soundcard.