1. A method of modulation encoding data for storage on a multilevel medium comprising: encoding a first portion of data using a first tier modulation code wherein the first tier modulation code maps a first portion of the data onto a first set of symbols; and encoding a second portion of data using a second tier modulation code wherein the second tier modulation maps the second portion of the data onto a second set of symbols and wherein the second tier modulation code has error correcting characteristics, and determining a third set of symbols based on the first set of symbols and the second set of symbols, the third set of symbols being suitable to determine nominal read signal levels from a multilevel medium; wherein improved error characteristics are realized for encoding data for storage in a multilevel medium.