From: Parsha Potpourri: Parshas Shemos (Friday, January 13th, 2012) at http://www.theyeshivaworld.com/news/Torah+Corner/114642/Parsha-Potpourri%3A-Parshas-Shemos.html
When the Baal HaTanya was young and newly married, he spent Rosh Hashana with one of the leading Chassidic Rebbes of the time. The Rebbe’s custom was that before the blowing of the shofar, all of those who knew how to blow would draw close to the Rebbe, who would teach them the mystical secrets and intentions to have in mind while blowing the shofar. At that point, the Rebbe would choose one of the assembled to blow the shofar for the congregation that year.
Shneur Zalman of Liadi, the Tanya
The Baal HaTanya joined the group, and to his surprise, the Rebbe selected him to blow the shofar. At that point, he was forced to sheepishly confess that he didn’t actually know how to blow the shofar. The confused and disappointed Rebbe asked him why he had falsely claimed to be capable in order to join the group. The Baal HaTanya answered that when Hashem initially revealed Himself to Moshe at the burning bush, Moshe asked for His secret name so that he could share it with the Jews to validate his mission. Yet shortly thereafter, Moshe declared himself unfit for the role due to his speaking difficulties. The Baal HaTanya used this episode as a source to similarly learn the Kabbalistic secrets of the shofar even though he would later have to declare himself incapable of using them to blow it.