This will probably be closed / moved to another site, but for the sake of putting in an answer,
I would like to know more information about pursuing the role of an Audio Software Developer:
You will need masters-degree Mathematics skills.
(Indeed, specializing in mathy stuff relevant to that field.)
What soft skills are useful within this role?
In the history of the universe, nobody has ever cared about the soft-skills of a programmer. The soft-skills of a programmer are as important as say the soft-skills of a bridge or a hydroelectric plant. :O
What technical skills are required to start at an entry position within a company as an Audio Software Developer?
(As you surely know, it's a really info-dense field. Just to get going y'all will have to memorize 30 or 40 blockbusters like this :O )
Is the type of employment typically short term or long term contracts?
Exactly as with any programming, you can have pretty much any job you want (short or long term) pretty much anywhere you want, and get paid unbelievable amounts of money, as well as shares, etc.
However note - the "first programming-job rules" apply to "speciality" programming (eg game physics, audio, whatever) just as they apply to everyday general programming: https://workplace.stackexchange.com/a/167673/22844
Indeed, it's even harder to get that first job as a "speciality" (say, audio) software'er.
Are the skills interchangeable between an audio software developer and a regular software developer?
In a sense, not really. To be a successful programmer, you have to be basically incredibly good. However, to be a (wildly) successful "math speciality programmer", you only have to be sort of an "ok" programmer, if that makes sense. Put it this way: if you get to a really high level, making insane™ money, as an "audio programmer", you would not be able to just move over - at that same money-making level - to being a "general" programmer. Note too that "general" programmers (for want of a better term) typically have insanely detailed - just bonkers, insanely detailed - knowledge of certain staggeringly boring / stupid / uninteresting arcane fields that are not, literally, about programming per se but are related (say, the minutia of bloody iOS table views, or whatever), which you will never know about (or want to know about!) any more than I will ever know the details of, you know, scales or tones or something that you know backwards!! Indeed, bonkers-money™ "general" programmers have to, just in passing, have elite expertise in a number of "side" (!) issues like sql, architecture, all that comp-sci nonsense, not to mention a gift for algorithms, and more: so yeah, it's not really interchangeable. If you follow US Gridiron, you will be like the Kicker - beloved, paid by the truckload, always in demand, Special, but not a "normal" football player, so "not really" is the answer to that one.
Thank you in advance!