Do you use up Bardic Performance rounds using a Doomharp?

[S'Daria]

Or you just need to have the class feature?

Doomharp:

Price 10,000 gp; Aura faint necromancy; CL 4th; Weight 5 lbs.
Made from bone and sun-dried sinew, this masterwork harp produces a vague sense of unease in anyone near it. If the owner of this item has the bardic performance class feature he can use it to perform a dirge of doom even if he is not of sufficient level to normally have access to that ability. A bard who can use dirge of doom and who plays the harp as part of his performance increases the effective radius to 60 feet.

CONSTRUCTION REQUIREMENTS
Cost 5,000 gp
Craft Wondrous Item, cause fear

[Archaeik]

Just from what you posted, yes. The Doomharp grants early access to the class feature, not remove the need to spend rounds of performance.