ingsy, when this type of omnidirectional microphone--a pressure transducer equalized for the diffuse sound field--is placed as it was designed to be, it won't sound nearly as bright as its on-axis curve would imply. You can generally subtract around 6 dB from the 0-degree graph as far as the actual sonic impression is concerned. This applies as well to microphones such as the Neumann (Berlin) KM 83, KM 130 or KM 183, or the Schoeps CMC 63 or CCM 3, when placed accordingly.
Microphones like this are designed to be used far enough away from the sound sources that most of the sound reaching them has already been reflected from various room surfaces, furniture and human listeners. They can be used as spot microphones, but they really go back to a very old-fashioned concept from the time before stereo: the idea of picking up an entire classical performance such as an orchestra concert (possibly with soloists and/or chorus) in a big concert hall from a single point in the hall, using a single full-range microphone. The well-known Neumann (Berlin) model M 50 was a leading example of this.
What's a little unusual about the Gefell M 960 as a recording microphone is that it has a large diaphragm. Nearly all other pressure transducers sold as music recording microphones have small diaphragms. The main result is that the inevitable disparity between the microphone's on-axis response and its diffuse-field response begins at a somewhat lower frequency than usual. That's neither a good nor a bad thing intrinsically; it's a characteristic which can be made to work in your favor with experience.
--best regards