Lots more on their YouTube channel. Uploader cartemarte1 explains:
Only 5 yrs and 8 mo, Cornelia is helping her older brother and sister to record one of their favorite songs. Rammstein has some amazing compositions, likeable to younger kids too.
Children Medieval Band:
Stefan (10) - vocal, guitar, violin
Olga (8) - keyboard
Cornelia (5) - drum, harp
The children have been trained with EarPower software.
(Thanks, Joe Sabia)