I've used Screech everywhere from Unrest to Mistmoore, Sol B, and Lower Guk.
Here are my two uses, and why I almost always have this song mem'd at 38th...

Soloing - I made a good part of 30th and some intermitant experience after that
level soloing using screech. I'll use Unrest as my example. I know Unrest inside
and out, having been a puller there since L18. At 30th, Carrion Ghouls and Dry
Bones were blue to me, so I would pull one outside to a wall, Chain it (Selo's
Consonant Chain) then hit it with Appalling Screech. As the monster slowly
walked away, I would chain again, then either hit it with 2 bellows or a heal
and a bellow. When I solo, I fight completely unbuffed. Hitting the monster in
the back saves me from taking alot of hits I cannot afford to take. If I pulled
2 monsters instead of just one, I charmed the one I thought would win, ordered
it to '/pet guard me' then equipped my lute and played Hymn while occasionally
replaying Charm to keep the monster on target. I used this method the first time
I solo'd the Undead Knight of Unrest at 36th, the second time I used a festering
hag to kill him for me (using charm, this was MUCH easier).

In a group - Screech is a devastatingly potent weapon in saving your parties
collective butt. In lower guk while fighting dar's, zol's and a few wan's (the
L36-46 range of undead froggies) we got trained by the hand room. The group
leader called for an evac, but we were all being mobbed, including the druid. I
hit screech. No less then 6 L40+ frogs fled in terror, and I was L36. All conn'd
blood red to me. The druid casted the evac successfully and we all escaped.

Example 2: In Solusek B (Nagafen's Lair) my group got trained while fighting the
Kobold King, a Solusek Kobold Shaman, and a Solusek Kobold. These are all 38+
monsters. add to that 2 GK shamen and 5 Greater Kobolds (35ish). I as a L37 saw
our main tank drop below 1 bubble and hit screech. WHAM! You see them ALL flee
in terror! Quite impressive to see the kobold king flee in terror.

My only warning: If you use this as an escape tool (group situation) and the
monster isn't snared, your group MUST zone. You will start a huge train
otherwise 90%+ of the time.

Last good use of this song - de-railing a train parked at the zone. I play it,
causing everything at the zone to flee in terror. I then zone. When the fear
wears off, they no longer have a target on their aggro list (I have zoned) so
they simply go home.

My astounding results even with higher level mobs are with a 165 brass skill
(for the last few levels). (max would be 190 right now)

Ariell ThunderWolf, Karana