Ignorant question about the sounds of simultaneous notes

[Rama777]

New bass player here

I suppose it may just be normal, but until I find out for sure it’s gonna bother me!

Especially on the lower strings, if I play two notes simultaneously, the beats between the notes are audibly distracting. Is that normal? To me it sounds like I stomped a vibrato effects pedal onto a guitar, kinda sorta. If I pluck the A fret on the E string, while plucking the A string, I get a steady sound of two A’s being played without beats. If I play an open E at the same time as fretting anywhere on the A string (aside from the 7th fret..), the beating makes an oscillating/beating/wobbly vibratoish sound that to me is, well, unpleasant. This beating effect is intensely pronounced on the lower strings, and much much less so on the higher strings. Is that just how it is on bass?

 

[Lenny JG]

I can't wait to read an informed reply here tbh if it happens.

 

[Rama777]

I was just listening to it again and it’s as if I’m almost not hearing either note sustain itself when played together because each respective note is fighting against the other and being drowned out by the war of the beats, or like a vibrato effect that borders on the discordant.

I was thinking it could be an effect of bad intonation, which I need to have corrected, but I don’t know. It seems to me like the only issue that would create when playing two notes together is dissonance, not a strong oscillation, unless again that’s just normal on low string dyads played on a bass.

 

[bholder]

It gets harder and harder to hear the harmony between two notes as the pitches get lower. Especially true for smaller intervals like thirds. So playing multiple note chords on bass can get muddy unless you're careful to stick to root and 5th on the E and A strings.

 

[monti2889]

Another thought is, the wave patterns of lower notes taking quite awhile to develop....so stepping away from the source may help, just a little.
Other than, just natural phenomena as mentioned in previous post(s)...this would also be more relevant if we were speaking of a single string oscillating...but pickup height does come to mind...not necessarily the/an issue in this case, but it may be something to be mindful of when the idea of output balance or oscillating notes comes up.

 

[LetItGrowTone]

EDIT: I googled for a "clean" explanation and found the below Wiki link, but felt I should explain this first part. I'm sorry if it sounds too simplified.

Play one note.
The graph of that note goes up and down, right?
Play a second note at a different frequency.
That note also goes up and down, but not at the same times as the first note does.
Sometimes the second note will *add* to the first note, and sometimes it will *subtract* from it.

That's what "alternately interfere constructively and destructively" means in the following paragraph.
The apparent note that results is called a "beat".

"Tuning two tones to a unison will present a peculiar effect: when the two tones are close in pitch but not identical, the difference in frequency generates the beating. The volume varies like in a tremolo as the sounds alternately interfere constructively and destructively. As the two tones gradually approach unison, the beating slows down and may become so slow as to be imperceptible. As the two tones get further apart, their beat frequency starts to approach the range of human pitch perception,[1] the beating starts to sound like a note"

Beat (acoustics) - Wikipedia

 

[LetItGrowTone]

Aside:
This is one of the reasons for conflict between 6-string guitarists and bassists. On a six string guitar these low frequency beats can sound like a bass playing along with the guitarist, and I can tell you that can be intoxicating to some people. But of course, when a real bassist shows up, real bass notes tend to cover up the guitarists beats, and this is hard to accept; from the guitarists point of view, his "larger than life" foundation drops out. Then what's left of the guitarist's act can sound mediocre, I can tell you.

A great illustrative example is Metallica, where the real bass guitarist is kept low in the mix to let the "larger than life" beats of the guitar be dominant (and a producer can augment this too). Try "Justice" above all.

 

[ctmullins]

Another thought is, the wave patterns of lower notes taking quite awhile to develop....

This notion, while often repeated, has no basis in any science. Waves don’t “develop” at all once they leave the speaker cone. They attenuate as they propagate, because a fixed amount of energy is spreading through more medium (air). But they most certainly don’t “develop”.

 

[Rama777]

Interesting stuff, thanks y’all! I was listening to the effect through 2x10’s and then thought I’d try it on a 1x8. It’s much more pronounced on the 2x10’s so clearly it’s more of a thing at lower frequencies. I grew up learning classical Hindustani music which utilizes drones a lot, so as a string player I tend to also utilize a moody drone string most of the time. I see that it’s just not a great idea to use the B/E strings for open drones, we’ll, at least not in conjunction with the A string. I like drop C# tuning so the effect is doubly pronounced.

 

[micguy]

We're talking about intermodulation distortion here. Whenever you present two frequencies to a non-linear system, (in this case, your speakers and your ears are the things that are most relevant, unless you have an overdrive situation happening) you get the original two notes, plus energy (extra notes, if you will) at sum and difference frequencies. The difference frequencies are the most troubling here, so we'll focus on them.

Let's say you play a low E and an octave above it - 41 Hz and 82 Hz. The difference frequency is....41 Hz (82-41). That's the same frequency as the lowest note you're playing, so there's no energy going to frequencies you didn't intend below the lowest note you're playing. The upshot is, if your rig handles a low note well, playing an octave above along with it is fine.

Now, try a fifth above the low E - a B. A musical fifth is a frequency ratio of 1.5, so the B is at 61.5 Hz, and the difference frequency is now 20.5 Hz (ish - I'm rounding numbers for the sake of slightly simpler math). So, you're asking your rig to play a note an octave below your low E. That doesn't go well - the speaker is driven very hard if you're playing loud, and it's going to manufacture harmonics (distort) at multiples of 20.5 and 41 Hz. What you hear is a mess.

OK, so go up an octave - Play an E, but not the low one - the 2nd fret on your D string, and also play a fifth above that - it sounds good. You're doing the same thing as before, but at twice the frequency, so you have intended notes at 82 and 123 Hz, and a difference note of...41 Hz - that frequency your rig can handle OK, so it sounds good.

The rule is simple - the further up the notes are that you're playing, the closer the harmony is that you can get away with - musical fifths, then fourths, major thirds, and finally minor thirds become viable the further up you play in frequency. This is (kinda doesn't need to be said, but I'll say it anyway) why bassists don't play chords - unless you're playing high on a 6 string or something - they just don't work most of the time.

It's Science (and unfortunately a bit of math, but I'm a Physicist, so that's stuff I actually get along with), not voodoo - and.....there's nothing wrong with your rig. Bigger, better rigs will do better at this, but you won't find one that gets rid of the problem completely - you have to be mindful of what you're playing and where.

 

[Cave Puppy]

Yep, that’s just how it is on bass. As stated, as the frequency gets lower, the sound wave structure (crests and troughs) get further apart, making it more difficult to line up to another low frequency played at the same time. The higher the frequency (higher on the neck) the shorter the waves, making it easier for multiple notes played simultaneously to “line up.” Super scientific I know. This may be way octave pedals usually can’t track (“see”) notes lower than an A.

 

[Zak TMD]

We're talking about intermodulation distortion here. Whenever you present two frequencies to a non-linear system, (in this case, your speakers and your ears are the things that are most relevant, unless you have an overdrive situation happening) you get the original two notes, plus energy (extra notes, if you will) at sum and difference frequencies. The difference frequencies are the most troubling here, so we'll focus on them.

This is information I didn't even know I needed to know, but explains something that's been puzzling me! Recently picked up an MXR Octave deluxe. Tracks great, sounds fantastic anywhere from D on the A up (actually C#, but whatev), but the muddy distortion of the lower freqs was so strange because I knew my cab's drivers could handle the low freqs, but I didn't understand what was happening or why the distortion was taking place. Now I know why!

Thanks @micguy & thanks science!

 

[Rama777]

No more mystery, awesome! As for the larger rigs handling things better, that makes sense, though I’ll restate that the effect is more pronounced on my 2x10’s versus my 1x8. But I assume that it’s because those competing frequencies have more of that oscillating tension at lower frequencies, which the 8” speaker doesn’t push through with nearly the amplitude as the 2x10’s, though for the hell of it I will cut the low frequencies on the amp to listen to the differences out of curiosity.

 

[legalbass]

This notion, while often repeated, has no basis in any science. Waves don’t “develop” at all once they leave the speaker cone. They attenuate as they propagate, because a fixed amount of energy is spreading through more medium (air). But they most certainly don’t “develop”.

I can't believe the myth that lower frequencies "take longer to develop" still persists.

 

[micguy]

Thanks @micguy & thanks science!

You're welcome.

 

[Lobster11]

Interesting.

I have a follow-up question: What if any difference would it make if your rig included a high-pass filter set around, say, 30 or 40Hz?

Edit: paging @micguy

 

[Killing Floor]

What @micguy said. This is a set vibration equations. Stay away.

 

[john_g]

Dont do that. Problem fixed.

 

[MrLenny1]

Yup, that’s the way it is.

 

[jmlee]

If the bass is in tune, and if the intonation has been carefully set for all the strings, one should hear very little by way of audible beats when playing octaves, fifths, major and minor thirds, etc. [N.B. I suspect that what the OP has described as a "vibrato" in the notes (varying pitch) is more likely a "tremolo (varying amplitude/volume) you would get without good intonation adjustment. I'm guessing that there's an intonation adjustment that needs doing on the OP's bass.