Among the Old World songbirds the Leaf-warblers and Spectacled Warblers are most intriguing. Their uniform outer coloration of green and yellow makes them difficult to distinguish in the field and even in museum collections. Within their morphological homogeneity they display a confusing wealth of forms in Eurasia, especially in the Himalayas and in China. Their diversity was long underestimated because mainly in East Asia their vocalizations remained unrecorded. Taxonomists had to learn that Leaf-warbler songs vary in small areas and thus may work as isolating mechanisms, preventing hybridisation of closely related populations. Only in the last twenty years did molecular genetics demonstrate that song differences may be not a joke of nature but often indicate different species – unrecognized due to their similar size and plumage. Hence the number of valid Leaf-warbler and Spectacled Warbler species has recently increased. This double CD presents songs and calls of most Phylloscopus and Seicercus species according to their actual taxonomy.