I now and then get emails from modders wanting to add custom music to their mods, asking what tools they should use to make their music sound "in line" with vanilla music so things don't sound too uneven. I thought I'd gather some answers and responses here for everyone to see - maybe it's of use to someone!
First of all, the first large batch of music for vanilla was made over a decade ago, which is a very long time when it comes to music software. Things get updated and replaced pretty frequently, so my own recollections from the 2010's are hazy at best! I can say that most of the early music, which includes most of the faction music and the core campaign music, used Reaktor by Native Instruments or Omnisphere (v1) by Spectrasonics for the synth sounds, and EastWest Symphonic Orchestra Gold for the orchestral samples.
For later tracks, like the hyperspace music, non-core campaign music etc. I turned towards hardware instruments and effects, where probably the Digitone synthesizer by Elektron is the most dominant sound source I've used, which I've also used for many of the energy weapon sounds. I often pair the Digitone with guitar pedals to make it sound different; for example the Boss CH-1 chorus is on most melodic synth sources and the Boss HM-2, DS-1 or MT-2 are used for explosions and ballistic weapon elements, sometimes combined in series.
Why don't I use software synths or software emulations of these very well-known pedals? At some point I made the observation that composers were basically all using the same synths and the same sample libraries all over, and came to the conclusion that I wanted to have, at least in some small way, "my own sound". I started testing out some less well-known hardware synths and found Elektron and the Digitone, and found it to be an FM synth that sounds completely unique with no software counterpart. I have a guitar background and had some pedals lying around that were really easy to pair with a hardware synth that has line outs, so I also discovered that analog distortion and analog chorus pedals can be an interesting addition to one's sound palette.
To end this post, here's a list of some of my most used plugins to this day in no particular order:
- All the Fabfilter effects, especially Pro-Q
- UVI Sparkverb (on tons of Starsector things)
- Eventide Blackhole (5% wet mix on most large sound effects to give them space)
- Soniccharge Echobode (used to make the Active sensor burst ability sound, one of my favorite sounds in the game)
- U-He Bazille
- GRM Tools
- Auburn Sounds Graillon
- Modartt PianoTeq
- Eventide Micropitch
- Native Instruments Kontakt
- Oeksound Soothe
- Soniccharge Permut8
- SoundToys Little Alterboy
Hope this is helpful!