Reply to Mixing in Key - How to figure out pitch of song that you pitch up/down

Hey everyone,

So i've recently been practicing by mixing in key because i feel it sounds better and it's easier to mix. I was wondering if i have a song playing at 128bpm, and i want to bring in a track thats at 124 - i have to pitch that up obviously, so how would i account for the new key of the song so i can still mix something in harmoniously.

Did i make sense? i hope so.

Thanks

-Mooook