The fastest tempo/beat sync I seem to be able to set is 50%

. - CORRECT

It can be slowed to as much as 6400% of the underlying tempo/beat

- CORRECT. So you could speed up a single Motion Sequence, and Slow everything else down (6400% worth of slow). It's a bit long winded, but at least you have the option.

How can I speed up the Motion Sequencer's cycling to (eg) 25%, 12.5%, 6.25% or even 3.125% of the underlying beat/tempo?

- YOU CAN'T.

Why? Because the software does not have this option. The minimum value (Tempo Sync) is 50%. It was not programmed in such a way to set it to 33%, 25%, 16.5% or whatever. That's a fairly straight forward, simple answer.

Why was it programmed with a 50% lower limit?
You would need to have a sit down with the Yamaha R&D team to get the definitive answer.

I do suspect the answer would be along the lines of "not musically useful". It's design intent is to be a control sequencer, not a Ring Modulator effect.

However, plenty of information has been provided in this thread on how you can increase the speed, independent of Tempo, Common or other Parts. You could, in theory, use mathematics to set the speed to some tiny fraction of the Tempo e.g. 1/128, 1/256 etc.

I did this. It works. To a point.

The problem is, beyond "musically useful" speeds, you lose audio resolution. So whether its 1/128 or 1/256.... its going to sound the same. It sounds like Brrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrr. (In case you were wondering). You can change pulse shape for some variations of brrrrrr, you can even get it whistling.

But then again, the Motion Sequencer was likely not designed for making brrrrrr sounds. Or whistle sounds. They have the FM-X engine for that.

I suspect the audio resolution is hardware limited, so a patch upgrade will not help.

@Anthony

I see you're going to need learn the difference between commonness and Common.

Upper case Common is part of Yamaha's terminology. I can see how you'd be confusing it with the merely common. Consider this: it's kind of like common sense versus microscopic focus on what is generally considered possible despite its being improbable, impractical and inconsiderate of the common.

Lower case common refers to those things that are most normally used in most normal situations, most commonly.

At a common rate of 120 bpm as the tempo, and arps set to their most common rate ratio, it is not possible to run the Motion Sequencer very fast.

Do you understand this?

Can you see how this might be a problem, or at least an inconvenient limitation, when using much of the other common features in a common way at common rates and ratios?

Can you also see how it's very easy for the programmers to make a minor modification to address this potential shortcoming?

@Andrew

This may or may not be of use to you.

Do a search for "Extended LFO". There is at least one video tutorial in SynthTips. It was a feature Released in 2.0/3.0.

As per previous posts increasing the speed of an LFO beyond a certain limit modulates the "carrier" tone, and whatever "parameter" was being modulated takes a back seat (becomes irrelevant) to some extent.

The Extended LFO allows you to increase the speed of the Part LFO to extremely high frequencies. There are also some basic options as to what can be modulated (Amp, Pitch, Phase Cutoff etc - you'll need to check).

The Extended LFO Speed can be modulated by the Motion Sequencer, using its usual patterns.

The good news, maybe for you, is that the Extended LFO is completely independent of Arpeggios, Motion Sequences, Grids, Tempo etc.

Not tried it yet, but I would imagine the end results will be fairly similar to having a super fast Motion Sequence.

@Antony

The extended LFO (which goes into the lower range of audibles) I mentioned two posts up, in this sentence:

This was part of the last update. A mode of LFO operation that includes some part of audible rates was added. It's a good addition for any sound designing usage of MODX/Montage.

Unfortunately the LFO doesn't help.

The things I'm doing can only be done with the Motion Sequencer, which offers custom "wave" shapes that aren't waves, at all, and work across multiple facilities inaccessible to the Part and Element LFOs.