I usually make mixings out of a MIDI file
I use Sibelius 7, load the midi, transform to a score, modifiy the score (dynamics, parts, arrangements,...), then export to midi, load the midi file to REAPER and assign instruments (either Kontakt, Additctive Drums or some sfz using sforzando)...
A recurrent topic over the years. I used to use Plugsound Box as a general purpose vsti (and vsti player at the same time). But ... it is discontinued for Windows 8
So I started to check the market (only freeware). I got Evansessence a 2GB soundfont, not as good and rich as Plugsound box, but I...
I am using REAPER on Windows 8 and a M-Audio Fast Track Ultra 8R to create a final mp3 audio track from a multitrack midi song.
I do it in 2 steps, using REAPER:
1) convert all the midi tracks to audio tracks, no pan, almost no effects, nothing,.. just as "raw" individual audio tracks
2) mix...