[LAU] BPM in music software [WAS] Re: Connect pipewire to running JACK server

Lorenzo Sutton lorenzofsutton at gmail.com
Fri Jan 28 09:49:35 CET 2022


Now... this is a very, very interesting new thread...

> 
> On Thu, Jan 27, 2022 at 5:27 PM Tim <termtech at rogers.com <mailto:termtech at rogers.com>> wrote:
> 
>     On 1/27/22 1:08 PM, Paul Davis wrote:
> 
>     Hiya Paul. Could you explain that a bit more?
> 
>     Human exponential vs. linear, I don't quite understand.
> 
> Let's suppose you are playing the simplest of beats, let's say you just play a note/tone at 120bpm. There's 0.5 seconds between your playing.
> 
> To do a linear speedup, you would gradually reduce the time between notes, maybe like this: 0.5, 0.45, 0.40, 0.35, 0.30 and so on

I think most software users have always 'adapted' linear tempo-changing 
and ramping interfaces to try and mimic somewhat 'realistic' human 
behaviour and indeed that can be challenging :-)

What I'm wondering is: when a software offers exponential ramps etc. 
isn't that just a user interface? i.e. how the software then calculates 
the ramp values automatically for the users and sets the BPM at certain 
instants depending on the granularity?
In that case I'd assume the software is then exposing the (calculated) 
BPM to e.g. plugins or a transport mechanism if it were the 'master'?


> 
> Alas, I have no specific info on this. x42/robin gareus might know more. Not many plugins care about the tempo map. The ones that do have a lot of potential for screwing up if they come with some baked in idea of "this is what accelerando sounds like".
> 

I know the above depiction might technically be very naive/unaccurate, 
but I wonder why would plug-ins crash based on the exponential.... It's 
a genuine curiosity, not a loaded question btw (this is LAD after all, 
and always a great place to learn for me).
So, I guess a quick tempo changes caused by a ramp for a BPM based 
plug-in, I would intuitively think might cause problems to a plug-in 
which is doing heavy calculations based on that BPM which is changing 
'too fast', but what would the difference between a very quick linear 
change or even very quick random changes entered by a user and 
exponential ones?

Lorenzo


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