Smith, who has led the Philharmonic since 1993, will step down when his contract expires at the end of the 2006-07 season. His tenure as music director is the longest in the orchestra's 42-year history.
In a statement, the orchestra said that Smith's new position would allow him to spend part of the year in Columbia, where he directs the Palmetto Opera, and "opens the door for him to conduct future Philharmonic performances." Meanwhile, Smith will be devoting much of his time to two festivals in Britain.
The Philharmonic will perform Smith's favorite works with during the 2006-07 season as it seeks a replacement.