The present document relates to audio source coding systems which make use of a
harmonic transposition method for high frequency reconstruction (HFR), as well as to digital

effectprocessors,e.g.exciters,wheregenerationofharmonicdistortionaddbrightnesstothe processedsignal,andtotimestretcherswhereasignaldurationisprolongedwithmaintained spectral content. A system and method configured to genemte a time stretched and'/or frequency transposed signal from an input signal is described' The system comprises an analysis filterbank (101) confrgured to provide an analysis subband signal from the input signal; wherein the analysis subband signal comprises a plurality of complex valued analysis samples, each having a phase and a magnitude' Furthermore' the system comprises a subband processing unit (102) configured to determine a synthesis subband signal from the analysis subband signal using a subband transposition factor Q and a subband stretch factor S ' The subbandprocessingunit(102)performsablockbasednonlinearprocessingwhereinthe magnitudeofsamplesofthesynthesissubbandsigralaredeterminedfromthemagnitudeof corresponding samples of the analysis subband sigral and a predetermined sample of the analysis subband signal' In addition' the system comprises a synthesis filte$ank (103) configured to generate the time stretched and/or frequency transposed signal from the synthesis subband signal'