Thanks for posting that, Amun.
I read a book a while back called "Bach's Feet", a history of organ pedals in Europe. (Seriously, there
is such a book and I actually
did read it.)
It's more than speculation that Bach used only toes when pedalling (it's often cited as fact) and even with that limitation, his pedaling was noted to be unbelievable to people that saw it up close. There were stories in that book I read of surviving church journals of the day and someone noting that they had hired Back to come in for a day to give their new organ the once-over and see if it met with his approval. Bach was known to be the only person who could thoroughly exhaust an organ's capabilities, so churches with adequate financial resources hired him to give his opinion on newly installed organs. Otherwise, they had no way of knowing whether or not they had bought a good instrument.
I'm not 100% sure of this since it's been over two years since I read the book, but if recall correctly, many organs of Bach's day really
couldn't be played very fast and at an advanced level with heels. The designs of the layout were nothing like an AGO organ of today. It was all toe-toe-toe.
I read that, today, one or two advanced organists have made a personal challenge of seeing if in fact all of Bach's compositions could be played all-toes, and they've demonstrated that it can be done. So between the design of the pedals, the fact that modern organists have shows that heels are technically not necessary to play all of Bach's stuff ... and the fact that
there are no surviving written references from Bach's era about anyone playing with pedals, there is more than a little consensus that Bach never played with his heels.
On the subject of shoes, I've had a melancholy thought these last few days. My uncle Jakob was a lifelong master shoe-maker, living in the Bavarian Alps in Germany. Unfortunately, he died about five years ago. If he was still alive today, how cool it would have been to task him with building me the perfect set of organ shoes ... shoes that are truly the thinnest suede "sock in the front", just like a dance shoe, with a proper heel in the back. And being family, I could have gone back to him over and over again until he had the design perfect. If he would have made me two or three pairs, I would have had perfect organ shoes for the rest of my life - made by my own uncle. Sadly, that will never be. It's just as well. If I did have such shoes from my uncle, they would probably be in a glass display case in my home and never actually get used.
On a different note, I do remember a funny segment in that
Bach's Feet book. At various points in history, the Germans and Italians have often had unfriendly relations. Way back in the day, the Germans considered the Italians "lazy" and the Italians considered the Germans "uncivilized" and "brutish".
The funniest (and most politically incorrect) story in the whole book concerns some German guy (in the mid or late 1600's I think) who made it his mission to introduce the German innovation of organ pedals to the Italians. He went to a major city in Italy that had an organ, and got that particular church up to speed ... having a full pedal board built and installed, and staying in the town long enough to give the house organist lessons in how to pedal properly. The Italians now had everything they needed to begin pedaling on the level of the Germans.
A few years later, that same pedal-evangelist went back to Italy to check on the church and to see how they were progressing with the pedals. Well ... he found that the Italians considered pedaling so difficult and so much work, that not only did they remove the pedal board they had been given, but they had a special console organ created that had two playing stations on it. The main manuals for the organist, and directly next to him (are you ready for this?), a separate
second manual where some apprentice organist would sit and play the bass line!
There was a picture in the book of that two-person organ (it still exists to this day), but it was a library book so I don't have access to it right now, otherwise I would post a scan of the picture. I've never been able to find the picture or that organ online.
Apparently that story made all the rounds in the German churches of the 1600's and reinforced the common prejudice of the day that the Italians were too lazy to play proper pedals.
Ouch!
https://www.amazon.com/Bachs-Feet-European-Performance-Reception/dp/0521199018