I'd like to use Sibelius with Sonar but they don't see each other unless they are both 32-bit. So I want to install 32-bit Sonar X1 on win 7 x64. But wouldnt there be a ram limitation? How do I get over the ram limitation? J-bridge it?

As far as I know, when using 32 bit it will only utilise 4gb of RAM.

Are you using ReWire?  If so, the latest SONAR X1 or X2 will support 64 ReWire clients.

Yea but that's just it, the 64 bit X1 version won't work with a 32bit app which is what sibelius is unfortunately. If I can wrap a VI such as Kontakt with Jbridge in 32 bit sonar to access more ram it will really solve this problem.

I see.  Well, then.  I'd say, if Sibelius interplay is important to you, you should just run the 32bit version.  Yes, there is a RAM limitation.  But in most cases, this can be handled with careful track freezing.

v7 of it has 64 bit support natively, I just looked.

Yes I'm aware of version 7. I really don't want to shell out for it though. I pretty much just got 6 few months ago and just started to get around to it. I think I'll probably just get away from Sibelius eventually and look at other alternatives

If you use jBridge you can bridge a 32 bit plugin for use in a 32 bit host on a 64 bit OS and get better use of the 4GM of RAM.

Study up on the finer details of the extra functions that jBridge provides.

Even if you are using 32 bit Sonar you should see some improvments in RAM available. Each 32 bit application can access up to the limit. Sonar and all the plugins running in it count as one application. But your OS and any other background software will not be eating in to this.

I am not sure, but I would have thought that a rewired application was a seperate process and would have access to its own 3.??GB.

As Mudgel suggests look into "sandboxing" using JBridge.