Anon. I think we found that the Yellow brick road was an actual speech given at the fbi. You can read it here: https://steemit.com/hillary/@flynnl1ve5/qanon-yellow-brick-road-speech-fbi-q-breadcrumbs
And there is a yellow brick road used in FBI training.
Read about it here.
I don't think it has anything to do with a concert.
pic related.
https://www.fbi.gov/services/training-academy/national-academy