The Sonar Studio version is cheaper than the Producer version. It comes with less tools and instruments than in the Producer.
Take a look in the comparison:https://www.cakewalk.com/Products/SONAR/Versions
The studio can make what you want but it doesn't come with TruePiano or the other instruments/effects that come with the Producer. Melodyne Essential is in both versions which you can use to convert one line melody (if not mistaken) from Audio to Midi including a singer's voice (this was the original purpose actually, like tunes adjustment). You can be sure of the details from the manual or Cakewalk forums.
Learning a new DAW is to commit a lot of time and effort to it. I don't know if Sonar is the best option for this task because I have never used Melodyne Essential (I don't have a need for it really). You might need to demo other DAWs which can convert audio to midi and then decide which one suits you more. There are like Ableton Live (no score editor), Cubase (only the top version has a full score editing), Studio One (no score editor) and maybe others that I forget now. I didn't mention Logic because I think you are with a Windows machine.
Personally, I don't use Sonar a lot but mostly Ableton Live Standard and Cubase Elements 7. Ableton Live doesn't have score editor, so I use Notion 4 ReWired with it. Notion 4 is a score editor which also can be used Rewired with Sonar and Cubase. Anyway, if you decide on Sonar X3 Studio, then you can get it with a big discount now in JRR Shop
(which I bought mine from there also, a downloaded license) for $119 but you can get I think additional 14% discount in the final cart if you write 'group' (without quotes). Oh, and the upgrade price from Studio to Producer is $149 which is cheaper than buying the discounted direct price for the Producer version ($329)