"Somewhat reasonable" is a good goal - it's something that most people can attain - even me!
I once heard an NPR host talk about being trained for speaking on the radio. The goal wasn't to make their voice sound like someone else, but to make their voice sound like the best version of themselves.
Singing is a very much like speaking. It's a bit traumatic - maybe
really traumatic - to find out what you
actually you sound like. But once you know what you sound like, you can start working on making yourself the best version of you.
Because you can't fix what you can't hear, perhaps the most important bit of software is Anything That You Can Record Yourself With™.
If you don't know how to sing, chances are that you're doing it wrong. It's like playing any other instrument - you can pick up bad habits that let you do some basic stuff, but end up undermining you in the long run.
The bad news is that software won't be able to fix your voice if you've got fundamental issues with your singing. These are things like:
- Running out of air while singing a phrase
- Having a voice that sounds like a throat filled with gravel
- Sounding like you're speaking instead of singing
- Going very flat before the end of a note
- Your voice "breaking" as you move from one note to the next
The reason it can't be fixed is because you've typically got changes of timbre that accompany pitch issues, and those changes in timbre are still there after pitch correction. The bad notes just sound like bad notes that are on pitch.
The good news is that the basics aren't that hard, and this sort of stuff is pretty easy to fix with practice. Once you've got the basics down, you'll have the tools to get that nasty stuff out of from your voice. You'll still sound like
you, but it'll be a better version of you, so to speak.
The
most important fundamental is breath support. Singing requires controlling the air. You'll need to know how to inhale, as well as control the release of that air. You might
think you have good breath support, but there's a reason all singing books start with this fundamental.
Once you've got breath support, you can work on holding out long tones on pitch. This means starting the note on the target pitch (instead of "scooping" into the note from below) and holding the note with proper breath support without going flat or sharp, up to the end of the note. With proper breath control, you'll be able to have a nice, clear tone through the entire note.
There's software out there that will help with this, but I haven't played with any. I
have used programs like the pitch correction in Reaper to look at what pitches I
actually sang, which can be both depressing and super-helpful.
The last step is to transfer the skill of singing held tones to actual music. Singing consists of sustained vowels that are interrupted by consonants. Making sure that vowels are supported and
sung goes a long way to making singing sound like singing.
With those fundamentals down, you should be able to clear up many of the issues that you might face as a singer. And that means that the few problems that remain
can be addressed with software.