I am thinking about Chopin, Johann Sebastian Bach or Mozart. They made the effort to pass on their knowledge to the next generation.
Bach, famously, wrote a whole book for his wife, some very simple pieces that every piano student has studied at a moment or another. Mozart also composed some short pieces. But his most famous effort is the sonata for piano #16 in C major. It is entitled “Sonata facile”. “Facile” meaning easy. And it is fairly easy. It explores what all student of the keyboard must know: Scales, arpeggios, simple harmonic progression. Mozart wrote that at the end of his life. His intentions were very clear: write something easy so that most pianists can play it.
As for Chopin, although the core of his work is some of the most difficult piano literature ever written, he left some room for the intermediate player. The famous Prelude in E minor is a must for all serious pupil of the piano. Chopin did not earn his livelihood by performing. He gave very few concerts and most were presented in small chambers. He was most famous as a composer and a teacher, and since he was obliged to teach many students, he composed quite a number of selections which can be played by students in the early grades without simplification.
I mentioned these three: Bach, Mozart, Chopin. There are others. Beethoven, Scarlatti, Bartok, the list goes on. I love to teach with the help of these great. They assure me that I am on the right path. It’s like having old friends help you climb a mountain.