You may not call me an expert on classical music. Regarding Friedrich Gulda I have my own experience.
In the beginnings of the 70ies I was invited by the “Bach Chorus” in Marburg/Lahn, my home town, to attend a concert of Friedrich Gulda. He already had made a side step adding to his classical concert a kind of “experimental design” with the group Anima.
On this wonderfully recorded and mastered 6 LP-set, Message from G., he plays the instruments like 200-300 years before with it’s traditional sound (LP 1, just look at the side notes – Clavichord).
The other concerts are a mix of classical and Jazz-oriented music.
It is Gulda at his best piano playing!!!