Feature suggestion: Constant ratio tempo ramp

Hi Midish developers,

According to Paul Davis, principal Ardour developer, studies
show that exponential ramps are much more natural to the ear
than linear ramps. 

AFAICT Midish uses linear ramp, changing the beat duration
by a constant amount each beat. 

Putting it out there that someone may like to implement
an option for exponential ramp.

Mail appended below.

Joel



On Thu, Jan 27, 2022 at 5:27 PM Tim <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

Problem is, it turns out that humans (even the musical among us) are not
very good at all at measuring absolute time. What we are good at is
measuring relative time, and so what actually happens is that we decrease
(or increase) the "time per note" by a constant *factor*. Let's say the
factor is 0.1. So now, the first note of our nominal accelarando is 0.45
long, but the next one is 0.405 then 0.3645 then 0.3285 and so forth. This
forms a natural exponential progression.

Put a different way, human performers do not speed up or slow down by a
constant amount per beat of an accelerando or decelerando, they speed up or
slow down by a constant ratio.

This behavior has been noted in several research papers on human musical
performance, and it is very, very difficult for most humans to do anything
else.

> And can you remember which types of, or specific, plugins would fail, and
> why? I'd like to investigate.
>

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".


-- 
Joel Roth