I thought this may be helpful to you.
In the Yellae Lama example, I was mistaken by referring to the song being in Gmaj scale.
However, as roentgen pointed out, it is an Em scale song.
Both Gmaj and Em are relatives, i.e. Em is the relative minor of Gmaj.
I just played the notes on the guitar and concluded it is a major scale (with one sharp - F#).
The below link explains the distinction, incidentally, with the same two keys - Gmaj & Em
Keys and Chords for Guitar
Excerpt from the website.
Every major key has a relative minor. The relative minor has the same sharps or flats as its major. Count up six from the major key to find the minor. The relative minor of C major is A minor. The relative minor of F major is D minor. The relative minor of G major is E minor. Look at the vi column in the table.
Someone might mistakenly say a song is in the key of G when it is actually in the key of Em. The key signatures are the same and the banjo might be in G tuning. If a song is in E minor the first chord will be Em, not G. The next chord will probably be D or one of the others in that key (the relative major).
As I was reading this, I was reminded about a useful post by roentgen, which talks about this -
Oru Jeevan -Geethanjali