<html><head><meta http-equiv="Content-Type" content="text/html; charset=us-ascii"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><div class="">Mmm, not really.</div><div class=""><br class=""></div><div class="">Wave shaping is along the Y axis only. For each cycle, the phase angles remain as they were, but every given Y value gets warped to the same new Y value.</div><div class=""><br class=""></div><div class="">Phase modulation is shaping along the time axis only. For each cycle, the Y values are unchanged, but their phase angles are warped to new values.</div><div class=""><br class=""></div><div class="">"Wave Morphing" might include both.</div><div class=""><br class=""></div><div class="">The subtle part is that certain kinds of waveshaping (again, Y axis only) can appear to warp the signal along the time axis, even though that didn't technically happen. "PWM" is an extreme and familiar example.</div><div class=""><br class=""></div><div class=""> -- Don</div><div class=""><div class=""><div dir="auto" style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><div style="color: rgb(0, 0, 0); font-family: Menlo; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px;">--<br class="">Donald Tillman, Palo Alto, California<br class=""><a href="https://www.till.com" class="">https://www.till.com</a></div></div>
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<div><br class=""><blockquote type="cite" class=""><div class="">On Nov 26, 2022, at 11:25 AM, David G Dixon <<a href="mailto:dixon@mail.ubc.ca" class="">dixon@mail.ubc.ca</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div class="">OK, I get it. It's just a subtle form of waveshaping. It's basically<br class="">linear FM where the modulating wave is at the same frequency as the<br class="">modulated wave, so that when the waveforms return to the same position they<br class="">are at the same frequency that they started at.<br class=""><br class="">-----Original Message-----<br class="">From: Donald Tillman [<a href="mailto:don@till.com" class="">mailto:don@till.com</a>] <br class="">Sent: Saturday, November 26, 2022 10:05 AM<br class="">To: David G Dixon<br class="">Cc: synth-diy mailing list<br class="">Subject: Re: [sdiy] "FM" Synthesis (was Re: Buchla 295 10-band comb filter<br class="">topology)<br class=""><br class="">On Nov 25, 2022, at 5:58 PM, David G Dixon via Synth-diy<br class=""><<a href="mailto:synth-diy@synth-diy.org" class="">synth-diy@synth-diy.org</a>> wrote:<br class=""><blockquote type="cite" class=""><br class="">I've struggled with this idea of "phase modulation" -- I don't really get<br class="">it.<br class=""><br class="">[...]<br class=""><br class="">Is any of that correct? If not, then I'd very much appreciate an<br class="">explanation of phase modulation -- specifically, what the hell is it?<br class=""></blockquote><br class="">You're way off. Not your fault; the goofy terminology has made this very<br class="">difficult to understand.<br class=""><br class="">Here's my zen explanation:<br class=""><br class="">You know that "subtractive synthesis" starts with a harmonically rich<br class="">waveform (ie., painfully bright) and runs it through low pass filters to<br class="">shape the spectrum dynamically.<br class=""><br class="">And "additive synthesis" starts with component waveforms and mixes them<br class="">dynamically.<br class=""><br class="">And "waveshaping synthesis" dynamically distorts the waveform, or more<br class="">specifically warping it along the Y axis.<br class=""><br class="">Well, "phase modulation" starts with a sine wave and warps the hell out of<br class="">it along the *time* axis, dynamically, with the help of a second waveform at<br class="">the same frequency (or simple ratio).<br class=""><br class="">Warping a waveform along the time axis means stretching this part of the<br class="">waveform, and squishing the rest. If the effect is subtle it ends up<br class="">resembling a PWM wave.<br class=""><br class="">If the effect is more than subtle, the stretches and squishes can go over<br class="">multiple cycles.<br class=""><br class=""> -- Don<br class="">--<br class="">Donald Tillman, Palo Alto, California<br class=""><a href="https://www.till.com" class="">https://www.till.com</a><br class=""><br class=""></div></div></blockquote></div><br class=""></div></body></html>