Adding a Circuit to Audio System for Recording and Playing Tapes at 1/4 Speed?

I have a Fisher audio component system MC-723BK. What I would like to do is to add a circuit that would allow me to record and play tapes at 1/4 speed thus making each side of a tape with a capability of about 3 hours or more, by the flip of a switch. This works well for talk shows only. Does anyone have a schematic diagram that would show this? Thanks.

By John from Chesterfield Twp, MI