It is not clear *where* your MIDI Tracks where initially recorded... you say they are in Cubase AI 10, but where were they originally recorded? You mention using MODX CONNECT... was that to move the Song into Cubase? Or did you record the MIDI tracks in Cubase?

Please give us an idea about the method used here, thanks. Because they should not have sync problems if properly recorded.
Were the vocals recorded (overdubbed) to these music tracks? If someone was singing to these MIDI tracks it seems something must have changed for them now not to match... ?? Please explain how the vocal tracks are now not sync’d with the MIDI tracks that were used to sing to... I guess the question is HOW did they get this way? Was there some transfer involved? (That is what is not clear).

Second question... “15/120 of a quarter Note”?
I have no idea how small an increment that is but sounds very small... what are trying to tell us with this fraction?

If you are using the Sequencer recorder in the MODX and recording vocals in Cubase, make sure you synchronize MIDI clocks. Cubase should be set to be the master MIDI clock source, which must be feed to the MODX on MIDI Port 1, and the MODX should be set to MIDI SYNC = MIDI
Cubase does not output MIDI Clock unless you set it up to do so.

TRANSPORT > PROJECT SYNCHRONIZATION SETTINGS... > MIDI CLOCK OUT > DESTINATION > “MODX-1 Port 1”

In the MODX, [UTILITY] > “Settings” > “MIDI I/O” > MIDI SYNC = MIDI

Once the two clocks are synchronized there should be no drifting as time goes on. All Tempo driven functions of the MODX are locked into the tempo set by Cubase.

Then there’s the issue of the Loop... if you are looping at the Measure line, and both items are synchronized properly, the only way for them to drift out of sync is if one of them is short a few clock ticks.

Bad Mister. Thanks for your response.

Here is some background.
Originally the instrumental was created in Maschine and exported to Cubase where the vocals were recorded using an M-Audio card. No problems were encountered when these audio tracks were played in Cubase via Yamaha Steinberg USB ASIO.

New midi tracks were then recorded in Cubase pointing to a MODX Multi/GM performance. Each MIDI track on Cubase was set to MODX-1 (in and out) and Channel "Any". The MIDI recording went OK, quantizing MIDI events as required.

After multiple loops within the Cubase locators, the MIDI would start to drift. Initially to counter the late start, I moved all midi events about 15 units to the left and they were on time for a while. That is what I meant by the 15/120. So a MIDI part starting at 5.1.1.0 in Cubase would sound better if started at 4.4.4.105 or even earlier.

I am recording all midi in cubase so cubase timecode source is internal with no destinations checked. MODX Connect has the performance saved for recall when required.

Thank you for your help. It is highly appreciated.

Bruce

Well, the MODX is just a Tone Generator here as far as MIDI is concerned... not Sequencing anything.

When you did the original MIDI recording, and added the vocals through the M-Audio Interface, what was the sample rate used? I ask because something changed when you moved the data...

MIDI data would not change but if you have a Sample Rate conflict, you’ll need to resolve that.
The MODX will operate at 44.1kHz, just FYI