If you mean the High “A” BELOW high “C”, that’s AWFUL!
Most of my students can hit the High “c”, even the guys. The “A” should be a piece of cake...unless the CONTEXT and the Vowel are what’s making it hard.
It is strange that the Hallelujah Chorus is associated with Christmas, since it is almost word-for-word from the Book of Revelation, (as is Worthy), and glorifies the Risen and Reigning Lord.
I know what you mean about a concert making you “high”. After something like that, the adrenaline has totally saturated your system. Who can possibly sleep!
And then, there is the Spiritual Aspect! WOW!
So, it’s all GOOD! :-)