Am I wrong is thinking that what you are creating is essentially a way to hand the computer a leadsheet and get back a complete notated arrangement for a given set of instruments?
If I am reading your description correctly, this honestly has very little to do with midi and is entirely a project about doing arrangements of an input piece and it starting and getting rendered back out as midi is irrelevant. You advertise doing harmonic analysis and without being able to see the rules/logic you use to accomplish that I can't really say if this is useful....it could be anything from some crap that makes everything a I IV V church-song progression to doing schenkerian analysis of the harmonies, progressions, and larger over-arching tonal progression. Nobody is going to pay you $150 for software that they can't even verify how it works when you are dealing with such a niche target audience (assuming you mean actual composers and not just minor arpeggios with the harpsichord effect and a drum beat lol.
Just so people reading this can get a better idea of what you are trying to advertise sell....what happens if I give it one hand of a simple Bach invention? What if I hack through a chord-melody version of 'Yesterdays' by Jerome Kern? Can it orchestrate me a big band version based on my right hand hacking out the melody and my left hand hacking out the i-ii-V-i and II-V-I cycles?
I apologize for being a bit harsh and hitting on a lot of shit....but when people post a webpage front for a blackbox application with a signup and payment plan and don't even share the code I assume they aren't in it for the 'hacking' and the 'show' and more in it for the 'pay me' and the 'now' and that the software will generally be shit.
but in all seriousness, if you say something as complex as that it analyzes harmony and harmonic structure and then orchestrates/scores it you need to give proof of how and what rules it is using and how I can explain to it that I want it to sound like baroque 4th species counterpoint or I want it to sound like (mostly ewww) 12 tone music like schoenberg, or if I want it orchestrated in a Classical/Romantic period style (even that is generous as if they are the same and Brahms and Chopin and Haydn sound the same)or perhaps a jazz style.......point being, you provided no code, no breakdown of how something as complicated as harmonic arrangement and orchestration (both harmonic and instrumental) is implemented and what sort of results one should expect.
If it is just a fun project then that is totally fucking awesome and I'd love to see it and help if I could...but then you shouldn't be hiding the code and thinking somebody is going to pay you $150 which is absolutely not going to happen for a black box claiming to do something more complex than I think most people here understand.
As somebody with a very high level education in music who has been doing software engineering for almost two decades and has thought about shit like this at great length.....I doubt you have created something useful to a real musician....if I am wrong, which I would love to be....then please tell me you have gotten actually trained musicians that are professionals (your friend that is 'really good at guitar' but can't read music and has never played publicly with other musicians doesn't count) or that you are a trained musician yourself and actually understand how this works. If you don't know what a Neapolitan chord is or what that roman numeral shit I typed was or the chord spelling shit I typed was then hit me up....I can help.