You can click on a track in the mixer and in the menu go to Track Settings | TimeBase. This enables the Half time, Double time, or Trible time, for the whole track. A workaround would be to load two of the same RealTracks to two separate tracks. Make one Half time and the other Normal, then mute them in different sections of your song in the Bar Settings, or in the Audio Edit window.


Best,
Chantelle