My common app essay addresses my interest in a specific major. However, for a certain school, I would like to apply for the school designed for a different major. I’m still debating between the two majors, but would it be odd to have a common app essay on a major yet talk about a different major on my supplemental essays (& apply)?
Yes, it’s a bad idea for your personal statement to address a major for which you’re not applying, @coogie36
They will notice. It won’t help your app.
Alright, thank you guys for your input 
You can change your personal statement with each application. Modify your personal statement for the school for which you want to use the supplement that mentions the conflicting major. GL!