Earlier in this thread, I posted this link to "Traditional Intonation On The Fiddle" - at Chris Haigh's, "Fiddling Around the World" site. 

A favorite excerpt:  

The whole approach to intonation [Scandinavian] is more deliberate and precise than in Irish or Old time fiddling, and there is more of a sense of using a completely different scale, rather than just modifying occasional notes in a standard scale. In conclusion, it is clear that there is far more to traditional intonation than just uneducated, sloppy playing.  Francis Roche, in 1927, summed it up beautifully in the introduction to the third edition of his tune collection. 

“....Those notes between the tempered scale, those are like rare rough gems, beautiful, sensual, emotional….they draw you in…and sometimes the tempered scale just feels clumsy and ill defined. I love how the voice will find natural harmonies and avoid the tempered scale, unless forced to follow that straight jacket by a more dominant and tyrannical instrument like a piano or full bore accordion. Sometimes it makes sense, when faced by such behemoths of the musical world, to quietly slip out and distract oneself by other means rather than being swallowed up by the abuse of power such things and their button pushing owners can wield. The low notes are the sound of the sea wind, and the high notes are the cry of the Banshee that it carries. Wither one alone is just a sound. Both of them together is an Irish sound” (Fiddle On Magazine).

So, MUCH MORE can be played on the Fiddle - curious?  

I've only begun learning about trad intonation of Eastern Music & the Maqams of Middle Eastern music, & posted some info in a few other threads. 

Middle Eastern Fiddle - Maqams & Microtones Thread

EQUAL temperament vs JUST intonation (PURE tuning) 

Hear the difference?  ...I like them both, don't mind the beating of the Equal - guess there's no hope for me. (lol) 

Here's a virtual 19 TET Keyboard to see how it sounds!

So weird to use this keyboard! 

🤔... anyone know that musescore could use plugins for microtonal music? 

Making Microtonal Music in MuseScore! 

This might be worth experimenting with.

Just intonation in the Renaissance 

Gets VERY interesting at 10:40 with a special 36-note-octave chromatic keyboard! 

🤔... "intonation is not only difficult in practice, but also in theory - true just (pure) intonation is the forbidden fruit we are only allowed to dream of" (?)

...if someone tunes their Violin using a YT "violin tuner" video that gives the pitch for ALL FOUR strings, instead of just tuning the A-string to 440 & then use it as a reference for the other strings - would that make the violin tuned to Equal temperament?  Do the people who make those 'tuner' videos make any temperament distinction?