Dispelling a Harpy's Song

[Nail]

- "Countering" is very specific, both effects disappear. The FAQ has an entry specifying this.

And "wow" is that sucker buried. It's in the 3.0e FAQ:

Q: When an opposite spell is used to negate an effect that is
already in place (such as using slow spell to counter and
dispel a haste spell), is the success of the dispel automatic,
or is a level check required? Does the subject or the caster
of the spell being countered and dispelled get a saving
throw?

A: Two opposite spells simply negate each other. No dispel
check is required, no saving throw is allowed, and spell
resistance does not apply.

 

[Nail]

So.....if a bunch of creatures are under the influence of the Slow spell:

• Casting Haste on all (or any??) creatures instantly dispels the slow effect.
  
• Cast a targeted Dispel Magic on any one creature, targeting the slow effect.
  
• Cast an area Dipel Magic on as many creatures as you can hit, and hope that a) the slow effect is the highest level effect active on them, and b) you beat the caster level check...otherwise your disple may remove friendly buffing spells.

Does that cover it?