You can choose from two morph controllers. These controllers manage how morph targets blend from one target to another.
A Cubic Morph controller is a TCB-style controller. It uses Tension, Continuity, and Bias controls much like the generic TCB controller.
The Cubic Morph controller manages only the interpolation from one morph target to the next. If you want to add Morph keys or change the morph target, you must use the Pick Targets and Current Targets rollouts in the Modify panel.
The Barycentric Morph controller is also a TCB controller like the Cubic Morph controller, except that instead of each key representing a single target, each key represents a series of weights for all targets. A Barycentric Morph key represents a new object which is a blending of all targets.
You can adjust each morph key to percentages of the available morph targets, creating subtle adjustments in the animation.
You can also click Add Keys in Track View to create new Barycentric Morph keys. The added keys contain interpolated values for all targets.