This is one of my first actually-useful programs. I wrote it back in high school as an exercise in learning both Turbo Pascal and music theory.
It's main feature is a chord formation screen where you can choose the key, scale, and notes that form a chord which you can then visualize on a virtual six-string guitar fret. It also displays the selected scale with intervals and the notes corresponding to the chosen key.
Other features include a musical and chord theory section, apparently written by a guy named Howard Wright in 1995 and a guitar chord and tab notation section, both of which I shamelessly ripped off from the Internet back in '99.
Oh, and don't forget to check out the Matrix-style rolling-letters screen on the "about" section. I'm still proud of it.
Everybody loves a screenshot:
Written by Cosmin Apreutesei in 1999.
ChordClopedia is free software.