I've just got to ask, what is a mechanical right?

The question comes from trying to understand this story:
Ringtone provider eXactmobile and a music rights organisation are headed for court in a multimillion-rand battle over royalties.

The National Organisation for Reproduction Rights in Music in Southern Africa (Norm) issued a summons against the provider in mid-August, and on Wednesday eXactmobile filed notice in the Cape High Court of its intention to defend.

Norm, an association of music publishers and composers, said in a statement that it is asking the court for an order that eXactmobile "must cease infringing the copyright of Norm's members" and pay royalties of 7,5% backdated to January 1 2006. It is also seeking R2-million in damages.

However, eXactmobile denied that it is not paying royalties for the ringtones it sells.

"There is actually a valid agreement in place between Norm and eXactmobile," said the company's chief executive, Davin Mole.

"This agreement provides the mechanical rights that we need to legally operate as a music seller," he said.

eXactmobile said it has tremendous respect for musicians and composers alike, and has no intention of avoiding the mechanical royalty payment.
full story from M&G here
Not being educated in these things, I would have thought the expiry of the contract would have meant expiry of the rights of eXactmobile to offer the material. But they claim this mechanical right. So what is that exactly?