recently i looked into getting a keyboard midi controller. we already have a piano but a piano doesnt have ports, so, i looked into getting a keyboard. however, keyboards are expensive, and i would prefer NOT to spend hundreds - potentially thousands - of dollars on somthing that would just be a little convenience thing for when i write songs. so, now i had the idea to take a microphone, run the frequencies through a couple calculations and output a midi or usb signal compatible with musescore and maybe garageband. i would have some switches on top for whether to output notation or audio or none at all, and maybe a couple potentiometers for tune and stuff like that. im not very experienced with audio though, and have no idea how to give a usb signal, never mind one thats compatible with other programs.
as you can probably tell by my description, im quite inexperianced in this field. i would like advice on which calculations to use in order to round to a perfect frequency, how to give a usb signal (thats compatible with other programs), and maybe some part suggestions. thanks!