‘The happy years’: an expression that is particularly apt for J. S. Bach’s period in Cöthen. Freed from the obligations that held him back in Weimar and not yet caught up in the Leipzig treadmill, Prince Leopold’s protégé produced masterpieces of such flamboyance that Benjamin Alard could not resist the pleasure of inviting some of his dear musician friends to join him around the splendid three-manual harpsichord by Hass.