I have a friend who uses Reason 5. I myself have Reason 6. We need to collaborate on a music file. So far the only way I know how to do this is to install multiple versions of Reason. The process to achieve Reason polygamy is as follows:
1. Uninstall all versions of Reason.
2. Install Reason 4 then move it out of "C:\Program Files\Propellerhead\" to another location.
3. Install Reason 5 then move it out of "C:\Program Files\Propellerhead\" to another location.
4. Install Reason 6.
5. Rename the Reason 4 folder to "Reason 4" and rename the Reason 5 folder to "Reason 5" .
6. Move the "Reason 4" and "Reason 5" folders back into C":\Program Files\Propellerhead\".
7. Make the appropriate Desktop and/or Start Menu shortcuts.
This is all fine and dandy, but of course since it's not a Propellerhead-sanctioned process it's not without its problems. There are registry conflicts (I'm on Windows 7) that force me to enter the serial number for each version of Reason every time I use a different version than last time, which of course is both tiring and time-consuming.
I propose that Propellerhead create a process by which one can comfortably install multiple versions of Reason and use them interchangeably, perhaps even simultaneously.
Alternatively, each version of Reason could be able to run in a "Compatibility Mode" which allows it to run as though it were an earlier version. It would block access to all new Reason features. On top of that there could be a Wizard that tells you which elements to delete from a .reason file to be able to convert it to a .rns file and work on it in Compatibility Mode.
I'm not sure what the community need for backwards compatibility is, but it would help this producer out very much. Please reply if you have interest in such a feature so that I and Propellerhead may know if it is indeed a development that might eventually be pursued.