QUAM transmitter from two DDS modules

So I was thinking about the possibility of making an AM stereo transmitter from two DDS modules put together. If you remove the crystal oscillator from one of them, it is possible to link them together to produce a signal phase shifted by 90 degrees. AM C-QUAM stereo is produced with a 90 degree phase shift. There are two things I'm not understanding about QUAM, though. Is it simply the left channel at 0 degrees and the right at 90 or vice versa (plus the 25hz pilot)? Or is there something else going on? The reason I think I'm misunderstanding is because various sources talk about L-R channel and L+R channel. What do they mean by that? Can I just do what I said earlier and will it work?