Is it the midi data generated from Reason (in the form of a Standard Midi File) or the audio from Reason that you are concerned with syncing?
In Sonar 6 Producer Edition you just plug in external gear to the designated midi out and go, but as I remember it wasn't so simple at the time of Sonar Home Studio 4. Not having a copy here makes it even more difficult to look at this question from the Sonar angle. You can do yourself some good by looking at the manual and seeing if it even mentions ReWire, which is what the Propellerheads call syncronizing two audio applications on the same computer.
Also, I understand that there is a certain charm to using a 20 year old keyboard for sequencing but if you learn to sequence on the computer you will find a whole new world of tools available to you as well as no more pesky memory limitations. For now, put the ESQ-1 in external sync/external clock mode. Back in the day keyboard workstations only supported midi clock as a sync standard, so if you have a choice in Sonar Home Studio choose that. Then you should be able to at least have sync between the computer and the Ensoniq, so connect the audio outs from both to your mixer and you should be ready to go.
If Sonar Home Studio does support ReWire, just follow the instructions to get both programs going at once. The outputs from the computer will have the audio from both Sonar and Reason.
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