This sounds like a job for The Music Curmudgeon!

 The Religious Curmudgeon posted this picture, which gained Robert's interest.

Robert wondered if she was related to Elvis.

TRC set him a challenge to find out who she was.

Then TC (really the same person as TRC) wrote this comment.

I didn't know that the boys learnt music theory in 3P!

I THINK THAT THIS EXPLANATION OF THE Amb9 CHORD WAS COPIED!

For those of you who don't know, the Amb9 chord fits nicely into a scale called the A natural minor scale.

As the boys in 3P were obviously taught, the A natural minor scale contains the notes A B C D E F G A.

Notice how all the notes come from C major (no sharps or flats). The chord uses the 1st, 3rd, 5th and 6th notes of the A natural minor scale, which is the 6th mode of C major. It is also known as the Aeolian mode.

Well, you might ask why the 6th note of the chord is called b6. There is another minor mode that comes off the second note of the major scale - D E F G A B C D. This is called the Dorian mode. We can extract the Dm6 chord from this mode - D F A B. The note that makes up the 6th degree (B) is a semitone higher than the F in the Aeolian mode, hence the F is a b6 (one semitone lower than a 6).

I left a comment.

But how did I know that Amb6 was used in the tune to the X-Files? Did I have to use the musical knowledge that I'd learnt in 3G?

NO!

I just downloaded Gillian's picture onto my phone and it had been saved under her name. It wasn't hard to connect her to the X-Files and I listened to the X-Files tune on YouTube.

I think The Religious Curmudgeon has been foiled on this one!

Ciao tutti.