Equal temperamant V Just intonation
General mountain dulcimer or music discussions
Discussions on temperament can get very involved.
Temperaments are directly related to note frequency, not note names. This is because a notes frequency, for instance 'A', can be an 435 or 445, or larger spreads. In order to set a starting point, the note frequency of 'A' is designated as the base reference point. Another part of temperament is that they define the spacing between adjacent notes in a diatonic scale. There are many more pieces to the temperaments puzzle.
A 'D4' is a 'D4' across all instruments, it may sound a bit different because of the material used to produce the note [frequency]. Just compare the note of the bass 7th fret to the open melody on a DAd tuned MD.
A D4 on an equal temperament MD may not sound/have the same frequency as a D4 on a differently tempered MD.
updated by @skip: 03/26/26 11:22:18AM

Instead of high to low, dAD, use low to high, DAd, it is more conventional for MD. For the other part of your question, always pluck the string just before turning the knob on the tuner. That way you know when you tune in the correct direction. As far as the F# A d, that would require a string change. You may be thinking of DF#A which needs different strings also. If you are tuned to DAA, just tune down, loosen, the middle string to F#.