Music ensemble rooms reach from small spaces for few musicians up to large ensemble rooms. Last-mentioned may include rehearsal spaces for brass bands, concert bands, amateur and professional orchestra. In this presentation a variety of recently built ensemble rooms for different music types and their acoustic design will be reviewed. It will be shown that well accepted large ensemble rooms do not neccessarily have to fulfill the extensive room volumes of at least 50 - 60 cbm / musician as required according to ISO 23591 „Acoustic quality criteria for music rehearsal rooms“. However, it turns out that it is more important to control strength G rather than seeking for an optimum reverberation time. In addition, it will be shown that the reverberation time for music rehearsal spaces recommended in DIN 18041 are generally consistent with the targets outlined in ISO 23591.