An apparatus for capturing audio comprises a first beamformer (305) coupled to a microphone array (301) and arranged to generate a first beamformed audio output. A plurality of constrained beamformers (309, 311) each generates a constrained beamformed audio output. A first adapter (307) adapts beamform parameters of the first beamformer (305) and a second adapter (313) adapts constrained beamform parameters for the plurality of constrained beamformers (309, 311). A difference processor (317) determines a difference measure for the constrained beamformers (309, 311) where the difference measure is indicative of the difference between beams formed by the first beamformer (305) and the constrained beamformers (309, 311). The second adapter (313) is arranged to adapt constrained beamform parameters with the constraint that beamform parameters are adapted only for constrained beamformers of the plurality of constrained beamformers (309, 311) for which a difference measure has been determined that meets a similarity criterion.