Performs gene set analysis (GSA) using various statistical methods, from different gene level statistics and a wide range of gene-set collections. The piano package contains functions for combining the results of multiple runs of gene set analyses. It also includes several functions for result visualization, including a network-based plot showing overlapping gene sets and their significance. Finally, piano also contains functions for the full analysis of microarray data, if the user wants a fully integrated GSA starting from raw expression data. piano is available as an R/Bioconductor package. Some of its functionalities are also available through the browser-based GUI BioMet Toolbox.