Invert the output of your LPF and mix it in equal proportions to the original signal. The lowpass'd signal will cancel out the low portions of the "dry" leaving higher frequencies.
Message
FW: [motm] Re: Time for an HPF!
2004-06-06 by Tkacs, Ken
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Message
2004-06-06 by Tkacs, Ken
Invert the output of your LPF and mix it in equal proportions to the original signal. The lowpass'd signal will cancel out the low portions of the "dry" leaving higher frequencies.