In the oral traditional cultures of Central Africa, the rules which underline the musical system are rarely verbalised: abstract concepts like “scale”, “degree” or “interval”, are not just non-verbalised, they are practically unverbalisable. Thus the study of musical scales requires the use of interactive experimental methods. For two years, a research-team leaded by Simha Arom (in collaboration with acousticians of Ircam-Paris) studies the untempered scales used by the Bedzan Pygmies in their contrapuntal songs and the Ouldeme in their hocket instrumental polyphony. The principle of the methods that we have developed is to make the musicians actors in the experiment, able to react immediately to the proposals of the investigators and to provide modifications of them, directly or indirectly.