An audio processing system (600; 700) comprising a multiband filter for providing a partially complex frequency-domain representation of a signal, the multiband filter comprising: a synthesis stage (691; 710; 810, 870) receiving a first subband range of a pure real first frequency-domain representation of a signal, the first frequency-domain representation being segmented into time blocks and comprising first spectral components representing spectral content of the signal in the first subband range, and outputting, based on the first subband range, an intermediate time-domain representation of the signal; an analysis stage (693; 720; 820, 880) receiving the intermediate time-domain representation of the signal and outputting, based thereon, a pure imaginary second frequency-domain representation of the signal, the second frequency-domain representation being segmented into time blocks and comprising second spectral components representing spectral content of the signal in the first subband range; wherein the multiband filter further comprises: a processor (640; 740; 860) receiving the first subband range of the first frequency-domain representation of the signal, a second subband range of the first frequency-domain representation and the second frequency-domain representation of the signal and combining these to output a partially complex frequency-domain representation of the signal, wherein: the synthesis stage is operable to release an approximate value of the intermediate time-domain representation in a time block located d 1 ≥ 1 time blocks ahead of its output time block, which approximate value is computed on the basis of any available time blocks of the first frequency-domain representation; and said approximate value contributes, in the analysis stage, to a time block of the second frequency-domain representation of the signal. a synthesis stage (691; 710; 810, 870) receiving a first subband range of a pure real first frequency-domain representation of a signal, the first frequency-domain representation being segmented into time blocks and comprising first spectral components representing spectral content of the signal in the first subband range, and outputting, based on the first subband range, an intermediate time-domain representation of the signal; an analysis stage (693; 720; 820, 880) receiving the intermediate time-domain representation of the signal and outputting, based thereon, a pure imaginary second frequency-domain representation of the signal, the second frequency-domain representation being segmented into time blocks and comprising second spectral components representing spectral content of the signal in the first subband range; wherein the multiband filter further comprises: a processor (640; 740; 860) receiving the first subband range of the first frequency-domain representation of the signal, a second subband range of the first frequency-domain representation and the second frequency-domain representation of the signal and combining these to output a partially complex frequency-domain representation of the signal, wherein: the synthesis stage is operable to release an approximate value of the intermediate time-domain representation in a time block located d 1 ≥ 1 time blocks ahead of its output time block, which approximate value is computed on the basis of any available time blocks of the first frequency-domain representation; and said approximate value contributes, in the analysis stage, to a time block of the second frequency-domain representation of the signal. a processor (640; 740; 860) receiving the first subband range of the first frequency-domain representation of the signal, a second subband range of the first frequency-domain representation and the second frequency-domain representation of the signal and combining these to output a partially complex frequency-domain representation of the signal, wherein: the synthesis stage is operable to release an approximate value of the intermediate time-domain representation in a time block located d 1 ≥ 1 time blocks ahead of its output time block, which approximate value is computed on the basis of any available time blocks of the first frequency-domain representation; and said approximate value contributes, in the analysis stage, to a time block of the second frequency-domain representation of the signal. the synthesis stage is operable to release an approximate value of the intermediate time-domain representation in a time block located d 1 ≥ 1 time blocks ahead of its output time block, which approximate value is computed on the basis of any available time blocks of the first frequency-domain representation; and said approximate value contributes, in the analysis stage, to a time block of the second frequency-domain representation of the signal.