Here’s a very useful chart to help you mix in relation to the song’s key. The tonal centre of a track is an important element to keep in mind especially when treating the bass in your mix.
With this table you can associate musical notes to their fundamental frequency, across the full range of the piano, and use it to match the frequency you want favour in your low end. You can also use it to zero in on offending notes that might be ringing excessively on some string instruments.
… and it’s also a bit fascinating to see musical notes in their Hertz values 🙂