Saswich where did that midi come from. I'd like a copy. Guitarpic you don't need to use every passing chord. If you just use the basic right chords the way the tune was written you won't hurt my ears. Ha ha.
I don't know if this will help, but basically for example in the key of C when you resolve to an F chord adding a 7th to the C like C7th adds intensity and it embellishes the sound before playing the F chord. Also a Fm or a F#dim is not what is considered a passing chord. Those are usually written in the song by an experienced musician who writes songs. There are many songs however that are written where the song writer doesn't know how to play a diminished chord, so they will just play a straight F chord through the complete measure. So, by adding the Fm or the F#dim in a song that hangs on the F chord, if its sounds better by adding the Fm or the F#dim it could be considered a passing chord or an embellishment etc.
A substitution is different. For example in C before resolving to an A7 many songs have a Gm7 added just before you go to the A7 chord. Now a substitution for the Gm7 could be a Bb6 which most average musicians would use and a Jazz pianist for the purpose of transition, sound, chord inversion to make it easier to play an A7b9 instead of an A7 may prefer to use an Em7b5 as a substitute for the Gm7 before the F chord change. If you look at the notes on the keyboard the Em7b5 has the same notes in it as a Gm6 which works before the A7 chord also. So, the Em7b5 could be considered an inversion to the Gm6 chord the same as a Gm6 could substitute as an inversion for the Em7b5.
This is not complicating if you sit down at the keyboard and fiddle around with this a half hour a day for a few weeks. You'll be an expert like Chas and all of the real musicians will applaud you, not just the audience who doesn't know jack that pays you all of those hundreds of dollars you made during your career, or you can continue to play the wrong chords all of your life and be like the neighbor who thinks he's a mechanic because he can change the alternator and put in a new radio and a pair of speakers. It the same damn thing. But hey as Hillary your next president says. "What the %#^*"@# difference does it make, HUH?
Good points and I will give it a try.
Like I said, I'm much more limited on the keyboard than I am on the guitar. And even more limited when playing the melody vs. singing along with the chords.
I've learned some stuff here and appreciate the feedback.