The 291e Triple Morphing Filter comprises three voltage-controlled bandpass filters that can operate independently or in parallel.

The amplitude, center frequency, and bandwidth of each filter may be independently voltage-controlled, and each can be modulated with externally applied signals.

The morphing capability might best be described as moving through a series of filter snapshots, with each snapshot consisting of a complete description of the filter parameters, and with each parameter continuously varying between snapshots. Morphing is accomplished with an applied voltage, or alternatively can be initiated with a pulse, with each stage’s time independently set. Up to eight stages may be employed.

All of the 291e’s settings can be stored and recalled using the 225e or 206e Preset Manager.