[sdiy] Envelope attack smoothing for drum question

Brian Willoughby brianw at audiobanshee.com
Sat Aug 22 05:09:54 CEST 2020


9 milliseconds would be an order of magnitude worse than a good drummer.

According to an article by Michael Stewart, from the October 1987 issue of Electronic Musician magazine, even a few milliseconds is enough to change the feel of a drum track.

At 130 bpm, playing as little as 7 milliseconds ahead gives the music a bit of "snap."

Playing 5 milliseconds behind the beat gives a "groove" feel, and 10 milliseconds is "in the pocket."

Synth bass is only about 2 or 3 ms behind.

Granted, not every live drummer is good enough to play in the groove or in the pocket, but those that can are consistently five milliseconds behind or ten milliseconds behind, respectively, as is required by the song they're playing. If the kick synth module is randomly 0 to 9 ms off, that's going to destroy the feel. It's hard to say from that article how precise the timing must be. Is a fraction of a millisecond in timing accuracy required? Is only one or two milliseconds of accuracy enough? No matter what, it has to be a small percentage of 5 milliseconds, or else the feel will not be as intended.


That said, larger delays are also common. Around 35 ms ahead of the beat makes a drummer sound nervous. 22 ms ahead and they have drive. 23 ms behind, and they're perceived as dragging. A drummer who's more than 40 milliseconds early or more than 34 ms behind is going to need to get a day job, or at least some more sleep. The point here is that although it takes several milliseconds of error before the drumming is noticeably "bad," in only take a very small shift for a funky drummer to impact a lot of magic in the sound. It would be a real shame to design a piece of kit for drumming that's going to randomly alter that.

Brian


On Aug 21, 2020, at 3:21 PM, Chromatest J. Pantsmaker <chromatest at azburners.org> wrote:
> would a 9ms delay be any worse than a professional human drummer?
> 
> On Fri, Aug 21, 2020 at 2:28 PM Mattias Rickardsson <mr at analogue.org> wrote:
>> Hi Jason,
>> 
>> On Fri, 21 Aug 2020 at 22:39, Jason Nanna <jasonnanna at gmail.com> wrote:
>>> Would delaying the trigger until an oscillator zero-crossing be a simpler way to synchronize?  Assuming a bipolar triangle, I don't think it matters whether it's rising or falling.
>> 
>> It would probably work, but would introduce undefined delays instead. For a boomy 55 Hz bass drum there could be anywhere between 0 and 9 ms delay, which I'd expect to be audible and untight...?
>> 
>> /mr
>> 
>> On Fri, Aug 21, 2020 at 3:33 PM Jacob Watters <jacobwatters at gmail.com> wrote:
>>> Right. The linearizing is for noise, but the trimpot is the important part for thumping. I added the diode part to my suggestion because it is a good practice that I often see left out.
>>> 
>>> On Fri, Aug 21, 2020 at 3:52 PM Dakota Melin <dksynth at gmail.com> wrote:
>>>> I think Jacob might be pointing out that if your VCA itself has DC offset problems that’ll thump as well. 
>>>> 
>>>> On Fri, Aug 21, 2020 at 3:41 PM Tom Wiltshire <tom at electricdruid.net> wrote:
>>>>> How does use of the linearising diodes hep with the offset click?
>>>>> 
>>>>> I agree about eliminating the offset as a source of the click, since if the VCA thumps, it doesn’t;t matter what signal you feed it, or even if you feed it no signal at all, you’ll still hear a click, but I don’t see what the linearising diodes have to do with that.
>>>>> 
>>>>> Tom
>>>>> 
>>>>> On 21 Aug 2020, at 20:25, Jacob Watters <jacobwatters at gmail.com> wrote:
>>>>>> You mentioned an OTA based VCA. I have experienced some clicking with these in the past. Use a linearizing diode and calibrate the 1k trimpot (https://i.stack.imgur.com/5drhW.jpg). That will rule out the VCA as the source of the click.
>>>>>> 
>>>>>> On Wed, Aug 19, 2020 at 5:42 PM Didier Leplae via Synth-diy <synth-diy at synth-diy.org> wrote:
>>>>>> We are working on an analog drum module that uses a simple envelope created from a trigger to control the amplitude of a triangle oscillator with a basic OTA based VCA.
>>>>>>  
>>>>>> We are having a problem with a slight clicking sound at the beginning of many of the drum hits. We think this is because the attack of our envelope is so sharp that the beginning of our drum hit looks like a straight jump from 0V to wherever the triangle wave happens to fall. Therefore the click is somewhat random in that it doesn't occur when the triangle happens to be low at the time of attack.
>>>>>> 
>>>>>> Can anyone suggest a simple way to deal with this, like adding a slight bit of attack time to the envelope? How could this be done without adding too many parts?
>>>>>> 
>>>>>> Thanks,
>>>>>> 
>>>>>> Didier




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