TLC can transpose the key of a song with a single click of the mouse. Check this out.

Two seconds later it's in the key of A and looks like this...

Is TLC uses intelligent parsing to "figure out" where the chords are.  You can type instructions, notes, comments and lyrics throughout your text and TLC will still find the chords!  The transposer is smart too.  If your transposed chords change size TLC repositions the chords so they remain over the right words.  It even handles transposing accompanying bass notes at the same time!