Yes, and I can tell you with 100% confidence that you're not going to write a good fugue until you've mastered species counterpoint in 4 or 5 voices.
There are even fugues with 2 voices.
Firstly, I doubt he wants to write fugues in two voices for the rest of his life. Secondly, fugue is only approachable after studying species counterpoint in at least four voices. If you've done it, you'll know why (even for two-voice fugues).
Yes the Eminor in WTC book 1, the difference between a 2 voice fugue and an invention is minimal with the second voice entering on dominant instead of tonic, and of course a bit longer and more developed usually.I would write some 2 part inventions first. Understanding harmony and how to have tones pass on strong beats and weak beats, along with suspensions.Forget Species, waste of time. I thought it was useless in college and I still think its useless today.
He Heh, well you guessed that right. I definately had the worst teacher in America but I still think 18th century counterpoint is more valuable to real world composition. Remember 17th century species does not deal with harmony today as we know it, but just with intervalic relationships. But whatever floats your boat, thats just my opinion.
The principles of species counterpoint are not bound by style if it is taught well.