They made quite a contrast on stage: the diminutive figure of violinist Alexandra Soumm, resplendent in bright pink evening dress, and the imposing black-clad bulk of conductor Peter Csaba. Both, however, are bundles of energy, which was deployed at full tilt in this performance of the Tchaikovsky violin concerto, closing the violin-laden programme of this year’s Sommets Musicaux de Gstaad.