The need for MELODIES (Model EvaLuation using Observations, DIagnostics and Experiments Software) arose when the study of atmospheric chemistry moved towards a unified approach. Specifically, the MUlti-scale Infrastructure for Chemistry and Aerosols (MUSICA) developed by the Atmospheric Chemistry Observations & Modeling (ACOM) Laboratory at NCAR simultaneously studies atmospheric composition across multiple scales. New models required re-writing of old-code to handle the variable resolution of model grids. Concurrently, measurement techniques and modeling are improving and becoming more complex, requiring updated comparisons at many different temporal, spatial and chemical scales. This provided an opportunity to create harmonized and consistent analysis tools for the atmospheric chemistry community. MELODIES is a project funded by NSF EarthCube that aims to address these concerns by developing a modular framework to compare model results and observations related to atmospheric chemistry. It aims to facilitate the use of diverse observational datasets in model evaluation. MELODIES combined with NOAA’s MONET to leverage shared goals and development. MELODIES MONET consists of components to manipulate both observations and model output, to allow for consistent quantitative comparisons with long-term and field intensive observations.