---------------------------- Original Message ---------------------------- Subject: Re: [music-dsp] � 45� Hilbert transformer using pair of IIR APFs From: "Ethan Fenn" <et...@polyspectral.com> Date: Sun, February 5, 2017 1:39 pm To: music-dsp@music.columbia.edu -------------------------------------------------------------------------- > Some very interesting references. > > I'm curious what uses people find for the Hilbert transform for in audio. > An instantaneous amplitude envelope, for use in compressors and other > envelope-driven effects? Or something else? using the analytic filter to get the instantaneous amplitude envelope (and, also, instantaneous frequency by differentiating phase) is something that works only with single sinusoids that are AM'd or FM'd. �for music, i think i would LPF the square of the signal (or run an efficient sliding max algorithm, we discussed this a while back) and work with that. it can also be used to measure phase shift from input to output in a noisy environment at specific frequencies (without the phase lag vs. phase lead ambiguity). but the reason i am most interested is in a frequency shifter. �like the ham radio single-sideband (SSB) thingie. �this is not a pitch shifter and detunes harmonic overtones into the inharmonic. �but it is totally glitch-free and can sometimes be handy to detune something slightly so that there is not a buildup of energy at a specific frequency (when there is feedback of some sort). �pitch shifters can do that too, but time-domain pitch shifters might have glitches for non-monotonic input and frequency-domain pitch shifters have a huge throughput delay. �also, this glitch-free frequency shifting can be slowly modulated. �might be useful for chorusing. �combined with a pitch shifter and pitch detector, you can shift harmonics without shifting the fundamental (i.e. pitch it up with a pitch shifter and then bring back down the fundamental to the original pitch.) -- r b-j � � � � � � � � �r...@audioimagination.com "Imagination is more important than knowledge."
_______________________________________________ dupswapdrop: music-dsp mailing list music-dsp@music.columbia.edu https://lists.columbia.edu/mailman/listinfo/music-dsp
