I'm making a software for marking a variable tempo to a piece

I don't know if this already exists but I've been working on a program that will let you adjust the tempo of a MIDI piece to a variable tempo you can mark by hitting the keys of a MIDI keyboard. You can even play the piece as you want it to be and then the program will adjust the tempo to your playing (after some edition, basically after leaving the piece as a single melody line). This would be specially helpful if you wanna compose many instruments pieces. I always felt it was unnatural to set the tempo by drawing a line. The question is, then, do you guys think this program is sellable? I've been working on it for several years already but I'm not sure if I should keep going, it's taking way too long. Is there any other software that does that?

There are click-to-tempo on many metronomes. Honestly, unless you're correcting for changes in tempo.... I just dunno, man.

What are you writing it in?

There's a software suite called SmartMusic that has a library of MIDI accompaniment files that will detect your tempo (regardless of instrument) and adjust accordingly.

I don't know if this already exists but I've been working on a program that will let you adjust the tempo of a MIDI piece to a variable tempo you can mark by hitting the keys of a MIDI keyboard. You can even play the piece as you want it to be and then the program will adjust the tempo to your playing (after some edition, basically after leaving the piece as a single melody line). This would be specially helpful if you wanna compose many instruments pieces. I always felt it was unnatural to set the tempo by drawing a line. The question is, then, do you guys think this program is sellable? I've been working on it for several years already but I'm not sure if I should keep going, it's taking way too long. Is there any other software that does that?

We've got a feature in Notion that is called NTempo which does exactly what you're describing.....

-Kyle