What's the difference between phasing and harmonic tremolo?

ChuckManual

They sound different, but the same, in equal measure.

I am confused - and my head hurts.

Please help...

menamestom

I don’t know but my Flint and P45 can sound very similar.

EricTheWeary

Odd really that harmonic tremolo and phasing and throw in rotary speakers, flanging and chorus have such different physical origins but in the digital world seem to have a gnat's hair between them at times. 

I think that harmonic tremolo splits the signal in two ( bass and treble) and modulates between them. Phasing, I think, does exactly the same thing but it can have multiple stages. So Harmonic tremolo and an MXR Phase 45 are doing basically the same thing. A Phase 90 or more complex phaser are doing something more, err, complex as they split the signal into multiple stages  Because they were originally produced through different physical processes accurate digital modelling would reflect that, how the modulation works is different ( in some way). Harmonic tremolo would ( wouldn't it?) have increased the number of valves that the sound passed through which adds to the overall compression/ degradation of the signal. Hopefully an adult will be along in a minute to explain it properly.        

Tadragh1

Harmonic tremolo, as I understand it, splits the signal frequency-wise. Phaser does not, right?

UnclePsychosis

The reason this seems confusing is because Harmonic Tremolo isn't really a tremolo effect in the purest technical sense. 

In "normal" tremolo, the volume is modulated directly.

In Harmonic Tremolo, the signal is split into two bands (high and low) and then the two bands are modulated separately before being summed back together, the effect being that high and low frequencies are alternately emphasised. This makes it sound a bit like a tremolo because the ear hears a "loud" (bright) sound alternating with a "quiet" (darker) one. 

A phaser also emphasises different frequencies at different times which is why they sound kind of similar to harmonic trem. 

ChuckManual

So... is Harmonic Tremolo simply a two stage phaser?

UnclePsychosis

ChuckManual said:

So... is Harmonic Tremolo simply a two stage phaser?

Kind of, but not really. 

I've not really thought about this too hard so I'm prepared to be corrected, but... 

In a traditional two stage phaser you have a single notch in the frequency spectrum which is smoothly "swept around". 

A harmonic tremolo is more like two fixed notches in the frequency spectrum that see-saw in amplitude. 

So you could probably build a really special case of a two stage phaser that would sound a lot like a harmonic tremolo by having it jump between two positions but I suspect that there are probably some subtleties in the implementation that would lead to other differences. 

ChuckManual

UnclePsychosis said:

ChuckManual said:

So... is Harmonic Tremolo simply a two stage phaser?

Kind of, but not really. 

...which is where I came in! 

ChuckManual

I'm starting to develop a twitch...

UnclePsychosis

ChuckManual said:

I'm starting to develop a twitch...

Don't worry about it too much.

Harmonic Tremolo is a time varying modification of harmonic content.

Phasing is a time varying modification of harmonic content, but done differently.

 That's why they sound similar.