OpenAL: Playing the same source twice at the same time?

I am building a sound library for my next iPhone application, and I have decided to use OpenAL for its low-level sound management, and memory usage (if I'm wrong, I am open to any alternatives).

My main problem is that I want the same sound to be played twice, without the second interrupting the first one. I was wondering how should I do that.

Other suggested that I assign the same sound source in the same buffer twice to achieve this result, but isn't that expensive in terms of performance and RAM usage? And is it true that it might work?

I appreciate any help given.

PS. I would also appreciate any sound library recommendations if there is a 3rd party sound library available for the iPhone...