I’ve followed Didi van Frits for years now. We even had the good fortune to be in Berlin visiting family at the same time and we got to meet in person. That’s was in June 2019. I dedicated a blog post to him in 2013
He has just published his book and I ordered the English version and it has arrived from Germany.
Here’s the link for the details.
About
“I’m 75 years old now. I’ve made a lot of music in my life since I was 12 when I started playing the banjo in a Dixieland orchestra. I studied theology, sociology, psychology, and finally philosophy. Of course, philosophy had the most lasting impact on me. But also painting, photography, caricatures (I love Sempe), and the weekly political debate or the science of history with its often frightening details. Where did I feel most comfortable? With the music.”
Videos at http://www.facebook.com/didi.vanfrits
You can hear my recording of him playing. Just a snippet of his playing guitar at his hotel courtyard when we met.
hopefully you’ll get a better sense of their method with the photo’s cropped version 
