Reddit mentions of Counterpoint in the Style of J.S. Bach

So I have spent the last month researching this exact subject! I have been reading every bit of info I could find on Fugue subjects, and analyzing more than I'd like to admit. Before I continue, I highly recommend buying a used copy of Counterpoint in the Style of J. S. Bach and read the first chapter, the chapter on inventions, and the chapter on fugue subjects, answers, and C.M.s

Anyhow, I'll share a couple of the most important things I found (Disclaimer: this is my own research, take this merely as an opinion)

1. Rhythmically, anything goes. You'll find just as many rhythmic patterns that attempt to build up motion (going from long notes to short notes), as you'll find subjects that are the opposite, or have almost no rhythmic variety.
   
   
2. Rhythmically varied subjects will often have the simplest implied harmonies. Rhythmically steady subjects will often be the most chromatic (secondary dominants). This appears to come down to tension.
   
   
3. The counter motive is pretty much always counter to the main subject in rhythm, note values, etc. The interplay of two very different, yet complimentary lines is what makes the fugue so fun. Also, it is nearly always invertible.
   
   
4. Fugue subjects of the baroque era largely use non harmonic tones in the most "textbook" (our textbooks today I mean, because they are written based off this old music) way. Nearly always prepared/resolved as expected, nearly always on an off beat, etc. Obviously there are a lot of exceptions to this rule, but you'll be amazed at how easy it makes analyzing subjects.
   
   4.5) This means most subjects are just outlining the harmonic formulae, but ornamented with smooth use of non harmonic tones.
   
   
5. The majority of subjects in the baroque area follow simple harmonic formulae. I V I. I IV V I. I ii6 IV V I, etc etc.
   
   
6. The implied high and low notes of a melody are nearly always going to be the dominant, the tonic, or the mediant. These will often have some sort of ornamentation that goes seems to break this (very often a neighbor note), but if you simplify and remove these obvious ornamentations, you will find it is nearly always one of those.
   
   
7. Tendency tones nearly always follow their... tendency!
   
   
8. Most subjects start on the tonic or dominant, and end on the mediant, tonic, or dominant, sometimes the 7th, rarely the 2nd, 4th, or 6th.
   
   Finally: the most important thing I learned
   
   
9. Even the greatest Fugue subjects played alone often sound... meh. And this is one thing I fought for so long. You can turn just about any melody that outlines I V I into an absolutely gorgeous fugue. Nobody is going to sing the subject from Bach's Fugue #6 from WTC book 1, and yet it turns into one of my absolute favorite fugues merely through it's use and development. Hell, Vincent Lo turned the Nokia Ringtone into a Fugue (yes, I know the nokia ringtone is based off a valse by Francisco Tarrega).
   
   So uhh... good luck! I write at least one new melody every single day as practice. 99% of them suck, but I get better every day. You should do the same :)

Yes as /u/nonnein points out, this is called implied counterpoint, and Bach was a true master of this and uses it in almost every piece. Listen to the Chaconne from the 2nd Violin partita for an absolute tour-de-force of this. If you know a little bit of music theory, then there's a great book Counterpoint in the Style of J.S. Bach by Thomas Benjamin that will give you some insight into it.

As to actually how Bach's mind worked, I think it's pretty hard for us mere mortals to reallllllly get it, but we can try.

There's an out of print book called Counterpoint in the Style of JS Bach

http://www.amazon.com/Counterpoint-Style-J-S-Thomas-Benjamin/dp/0028702808

I've only worked with the canon chapter out of that one, but it was really really well done - knowledgeable but also well written (kind of a rare combination int theory books ;)

My understanding is that a lot of the content was republished in "The Craft of Tonal Counterpoint" http://www.amazon.com/Craft-Tonal-Counterpoint-Thomas-Benjamin/ (same author)

I haven't used this book yet, so I can't recommend it. But hopefully your will library will have it?