Abstract We analyze a recently proposed distribution, defined as the ratio between three- and two-particle energy-multiplicity correlations, which probes the connection between colour and hadron multiplicity flows in e +e − annihilation. This connection is due to QCD soft gluon interference and is the same dynamical feature involved in the “string” effect in three-jet final states. The quantity we analyze does not suffer from any of the limitations of the string effect. It does not require any special event selection or jet finding algorithm, thus it provides a high statistics test of the colour connection. Although energy-multiplicity distributions are infrared singular, the ratio we consider can be calculated completely within perturbative QCD. Due to its infrared sensitive structure, the perturbative parameter is √ α s rather than α s, thus corrections are large. We find that the first next-to-leading corrections are relatively small (of the order of 10–20%) except for two contributions: (i) the singular behaviour for vanishing angle between the two registered particles is screened by an anomalous dimension obtained by resumming higher order leading collinear logarithms; (ii) a hard elementary processes, not present to leading order, gives a numerically enhanced contribution which is comparable to the leading term. Further higher order corrections are not expected to be large.