There, there's about seven different qualities that are highly associated with someone's credibility, trustworthiness and perception of leadership when it comes to vocal qualities. The research around this astounding. 

For example, Duke University did a study of almost 1000 CEOs.  They found on the topic of pitch alone, CEOs who had a lower pitch to their voice, had more tenure, commanded larger companies had more perception of credibility and leadership.  They also made more money, on average of an additional $180,000 per year.

While vocal tone is hard to change it is not the only element of your voice that can contribute to your success.  Other elements, including tempo, which can be learned are  can impact perceptions of credibility, leadership, trustworthiness is tempo.