A 90% of the Bandola Llanera performance can be executed on the key of D major (along with its relative B minor) and D minor (along with its relative F major). In the case of the Bandola Llanera, while the all 5ths tuning is basic as in the mandolins, it tunes usually from low to high not as G, D, A, E, but as A, D, A, E, by two semitones elevated on the 4th string. On the other hand, the other bandolas tune as G, D, A, E, played very often on the key of G major.
The scale shown below can be called “D major scale” starting with D (0/3) and “B natural minor scale” starting with B (2/4).
Note: (0/3) means the open string of the 3rd string and (2/4) means the 2nd fret of the 4th string.
Now you can try for yourself using the above image and tabs as your reference material. Familiarize yourself well with this scale as it is widely used in the world of the Bandola. Give it a try!