Symphony No. 8 (1968). Roger Sessions /but not simpler/

Einstein:

Everything should be made as simple as possible, but not simpler

Ok, the attribution of that quote turns out to not be so simple. The Quote Investigator:

The New York Times published an article by the composer Roger Sessions on January 8, 1950 titled “How a ‘Difficult’ Composer Gets That Way”, and it included a version of the saying attributed to Einstein [AERS]:

I also remember a remark of Albert Einstein, which certainly applies to music. He said, in effect, that everything should be as simple as it can be but not simpler!

The quote trail continues on for 20 or so paragraphs.

To keep the writing of this post as simple as possible, here's the first YouTube video that pops up for Roger Sessions: