Somewhere between price and performance sits the secret to a harmonious outsourcing relationship - if you can convince your partners to sing the same tune.

If Accenture Associate Partner Dr Jane Linder is to be believed, good outsourcing relationships involve a lot of tension, a suggestion of miracles and perhaps a little music.

Linder, from the US-based Accenture Institute for High Performance Business, is one of the authors of the report "Control: Getting it and keeping it in business process outsourcing". Overall, the report suggests that, as the market for business process outsourcing (BPO) grows rapidly, particularly in the Asia Pacific region, relationships and control mechanisms will need to grow concomitantly more sophisticated. The report suggests this means executives will need to:

• cultivate a broad view of control, which means incorporating indirect nurturing mechanisms in addition to traditional direct supervisory controls

• launch broad controls early in the BPO initiative

• use controls dynamically to maintain ongoing BPO momentum, which means "alternating traditional and broader mechanisms to create a healthy tension".

That last word causes problems for some people, and Linder admitted to CIO it might not be the most apposite choice of words, redolent as it is of stress and uncertainty. "Tension is an interesting word. Maybe it's the wrong word," she says, "but balance isn't good enough. It's not balance, because there is tension.

"Think about it personally. Let's say today we're going to have to sit down and hammer out an agreement where I've got to pay you money for something. That's one kind of conversation we're going to have. And by the structure of it we are on opposite sides. The more I pay you, the better off you are and the worse off I am - it's a zero sum game.

"The next day, you and I, the same two people, are in a conversation of how we're going to solve a hard problem in our process together. Now we're on the same side . . . we'd better be on the same side!

"The two people have to be able to switch between those roles, so that's why I talk about tension. There are all sorts of things going on between us that have to be navigated and made to work."

Others with experience in developing such relationships agree. Drawing on comment from three corners of the outsourcing relationship - customer, supplier and legal - Ian Harris, commercial manager for customer operations at Vodafone, calls it "a creative tension"; Scott Petty, COO of Dimension Data, calls it "natural conflicts"; and Nick Abrahams, partner at law firm Deacons, describes it as a "marriage", which is much the same thing.

In other words, tension is a positive force, a kind of potential energy that keeps a relationship strong and innovative. Perhaps "torque" is a more appropriate word.