If you're talking about something like automation gain, then no. There is no realtime playback of the sequence and recording of keyframes.
However, keyframes can be quickly added by simply selecting a range in your audio and then dragging up or down to adjust the volume of that range. FCPX will automatically create 4 keyframes and you can adjust them manually after as well.
you can also option click the volume line to add keyframes.
Andy
http://www.timesavertutorials.com