[sdiy] Harmonic bandwidth

[Ben Lincoln]

Just to be clear, if I am making some sort of giant error, I'd 
definitely like to know about it. Part of the reason I subscribed to 
this list is to break the rust off of my music/audio knowledge.

Ben Lincoln wrote:
> I suspect that I am not using the right terminology here. I have a 
> background in music, but I haven't worked much with audio in a number 
> of years. When I describe altering the phase, I am not meaning that I 
> am inverting signs (necessarily). I mean that I am adjusting the 
> offset of one or more of the component sine waves by less than an 
> entire cycle of that wave, so that its phase relative to that of the 
> fundamental frequency is different.
> For example, I created a sawtooth-like wave in Audacity using 32 sine 
> waves (100 Hz fundamental and then the next 31 integer harmonics) - so 
> more accurate than my Seiko DS would produce, but not as accurate as I 
> could get out of my K5000. It's got an exponential curve instead of 
> being a linear line because I didn't want to take the time to adjust 
> the amplitudes of each component properly. In order to make the effect 
> as apparent as possible, I picked a random offset (again, of less than 
> one cycle) to adjust each of the harmonics to, rather than just using 
> one or two like I did earlier today.
> Here's an mp3 file of the original versus randomized phases:
>
> http://www.eventualdecline.com/Normal_versus_Phased_Harmonics.mp3
>
> Besides the obvious difference in sound, If you look at it in a 
> spectral view, you can see that the two sections are very similar in 
> terms of their basic content, but the second section appears 
> "smeared". So if I am using the incorrect terminology, I think that 
> the author of the PADsynth software is using it in the same incorrect 
> way, because that is what I took away from his discussion of "harmonic 
> bandwidth".
>