Sounds of natural landscapes at dawn and dusk are modified and have a particular quality. Pierre Huguet had recorded this phenomenon in various West European natural habitats; thunderstorm in the Ried part of Alsace and an evening in a Vosges forest, both in north-east France, a dawn chorus in an Alpine forest (at 1,100 metres altitude), the atmosphere at dusk in a lagoon reedbed in the Guadalquivir delta in Andalusia (south-west Spain), an evening in a Camargue marsh (southern France), dawn in the Black forest (Germany). Patrick FREMEAUX