Mosaics are orbits of partitions arising from music theoretical investigations. Various theorems from the field of "enumeration under finite group actions" are applied for enumerating mosaics. In other words, it is demonstrated how to enumerate G-orbits of partitions of given size, block-type or stabilizer-type. Key words: Combinatorics under group actions, applications in music theory, enumeration of partition patterns. 1 Preliminaries Applying methods from P