How much MIDI latency is normal?

[Automation]

First off, I realise my question: "How much latency is normal" is very broad so please allow me to explain.

I have a lot of synths and keyboards and some of them have their own USB connections directly to my DAW and some have only DIN and are connected to a MIDITECH 8X8 hub which is connected via USB 3.

As far as performance goes time wise I can't say I notice a difference between USB connection and DIN. Also, some synths have more latency than others which I am sure many of you have also experienced.

My question is (and this is coming from an untechnical brain like mine), does latency typically only have to do with how long the first note in a sequence takes to get recorded in or played back, or does latency effect every note in the sequence?

I always assumed that after I moved my recorded synth tracks forward 3-10 ms so that the first note in a quantized sequence was at exactly bar one, that every other note in the quantized sequence would be moved relative to that and as a result, perfect on the grid.

But, today, after programming percussive sounds on my Prologue and recording them as audio I noticed that while the first note in a sequence was right at bar one (after I moved it there) the following notes were often a few ms late or early down the line.

Is this normal and is this what is referred to as MIDI latency.

If my question is blaringly obvious to some of you I hope you will go easy on me. I am learning as I go, and I am a guitarist recently turned synth enthusiast

Thanks for any tips or insights.

[OpAmp]

Hi, you are probably indeed suffering from MIDI latency. But it is complex...

I don't know how it goes for devices connected straight away through USB, but at least for those connected through DIN the following applies.
The signal over the MIDI cable is in fact a UART signal at 31.25kbit/s. One note on message takes 3 bytes (sometimes 2 might be used as well). Together with start and stop bits per bytes, one message takes 30 bits or 0.96ms. Suppose now you hit a chord of 3 notes, although you hit all notes together, they will be spaced by 0.96ms when traveling over the wire.

Second depending on the implementation of the synth, it may not process the events right away, but only at certain intervals. Till the start of an interval, the notes are queued up to be played. Depending on the moment of arrival vs the intervals, the notes may have different latency.

Probably, other effects might be playing as well in this variability of the latency.