Alex, I'll just address your first question here and also encourage you to join the Modern Chord Style Players Group here.
When he performs, Steven Seifert rarely uses his thumb. Aaron O'Rourke uses his more often, but still not a lot compared to the rest of us. But importantly, both of them teach chording using the thumb. And most of use all our fingers.
The reason Seifert and O'Rourke don't use their thumbs that much is that they use their ring finger (Seifert) or their pinky (O'Rourke) to barre across all the strings, allowing the other fingers to fret strings above the barre. So in DAd, whereas I play the 335 G chord with my middle, ring, and thumb, Aaron just forms a barre with his pinky at 3 and then uses his index finger on the 5.
One thing to keep in mind is that if you don't use your thumb, the dulcimer can sit straight across your lap, kind of perpendicular to your legs. But if you use your thumb, you will want to angle the head of the dulcimer out over your knee more. This is easy to demonstrate and harder to describe, but the basic idea is that you want a relaxed angle for you fretting hand. I often change how far out the dulcimer is angled depending on how much I use my thumb in a given song.
Personally, I think the best approach is to be flexible, making sure you are able to use all five fingers, and then choosing the fretting hand attack that best fits a given arrangement.
For the record, I played the guitar for decades before discovering the mountain dulcimer. I think of the right hand as playing the guitar and the left hand as playing the piano. Maybe that helps. Maybe not.
--
Dusty T., Northern California
Site Moderator
As a musician, you have to keep one foot back in the past and one foot forward into the future.
-- Dizzy Gillespie
updated by @dusty: 06/14/25 10:08:43PM