This month, Andrew Litton will conduct his final concerts as music director of the Dallas Symphony. His 12-year tenure with the orchestra has been rocky at times, and in recent years he has clashed openly with local critics and the DSO’s president, but he is also credited with keeping the orchestra in the recording business at a time when most other American ensembles couldn’t buy a record deal. The DSO has also had a lot of turnover in the last decade, and “Litton has hired a third of the DSO’s current roster of musicians. That may be his greatest achievement.”