A third option for an older 32bit DAW, or one that does not accept HALion as a ‘plugin’.
Install a set of virtual MIDI ports. If you do not already have some, loopMIDI is a good free option for a Windows system. Streaming MIDI over your LAN using rtpMIDI might come in handy if you’d like to sync multiple computers instead of running everything on the same one.
From there it is possible to assign the stand alone version of HALion SE to a set of audio ports, and use the virtual MIDI ports to direct the MIDI output of tracks in your DAW to the stand alone HALion instance. Possible options to route the audio of a stand alone HALion instance back into a DAW will be addressed last in this post (jack2/ASIOALL/etc.).
If your old 32bit DAW supports rewire, you could grab the early bird demo for Bidule, host HALion a 64bit bit instance of Bidule, and connect that to your DAW via Rewire.
Tips for audio routing among different applications.
This scenario almost always works. You could hard patch it with actual patch cables (connect the respective Audio outputs back into the desired audio device inputs required to get a signal into your DAW and on its mixing console). This is the easiest and most reliable solution I know of. Personally, I like to take advantage of the SPDIF ports on my audio cards in cases like this.
IF your DAW supports ASIO audio drivers:
AND your audio device supports ASIO,
THEN jack2 can allow you to reroute your audio matrix through an ASIO backend. In short, you can build a kind of virtual patch bay for your audio signals. Establish a bus in the DAW listening to a given set up inputs in your jack2 matrix, and have the audio from the stand alone Instance of HALion routed there. Jack2 can also be taught to stream audio over your LAN.
IF your DAW supports ASIO
AND IF your audio card does NOT have native ASIO drivers
THEN ASIO4ALL can be used in place of the generic Steinberg ASIO backend to get a more flexible ASIO configuration, including but not limited to aggregating audio devices into a single ASIO driver. This also allows jack2 to work with audio devices that do not natively support ASIO. It can also come in handy if you would like to ‘aggregate’ a number of inputs into a single driver back-end (I.E. Merge your USB mic into the DAW, while still being able to use everything on your other audio devices). While possible, I do not recommend aggregating ‘outputs’ if synchronization is important (outputs will drift out of sync over time if they are not sharing the same audio clock).
For a non ASIO setup, other virtual cable options such as (VBA and VAC) exist for WDM, MME, and other types of Windows audio drivers.