MIDI playback differs depending on number of times a region loops

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MIDI playback differs depending on number of times a region loops

On the first pass of a 4 bar loop, all notes sound correctly, on the second pass beat one of the fourth bar is dropped entirely. When the loop is then shortened to just the fourth measure, the missing chord from the previous playback is dropped the first time before then loop plays normally four times, after that, only the highest note of the chord in question will sound.

The problem is always present in bounces, and even if I delete the region and copy and paste it in from elsewhere in the song where it plays correctly, or recreate it on another track or in an entirely different project by right clicking it in or playing it in with a keyboard that was just returned to factory settings the problem persists...

Not in the video, but curiously, if I switch the piano sound from the stock Logic Steinway sound to a Native Instruments piano plugin the same chord is affected, but in an entirely different way - instead of being dropped, the chord becomes roughly a 16th note, and the key velocity seems to spike to 127 even though the list editor still shows the chord being a quarter note with the velocity steady at 80.

If I drag the region in question to another point in the song it's glitchy in a slightly different way, even if I don't move automation (there's no automation on the track put there by me, or displaying, not that I know of a way to make automation work differently on different passes of the same exact section), if I copy and paste, it does bring the issue with it, even if I don't copy automation.

Unfortunately, it seems that the issue is not limited to note length, key velocity or level, all editable parameters of any virtual instrument or effect seem subject to the changes. I have recreated affected projects from scratch on a second computer and had the same issue, even though the only thing that the two computers had in common was that I had to log into my App Store account on the second computer to download Logic.

Any help would be greatly appreciated.

Here's the clip on YouTube (the option to embed video is grayed out for me):

https://www.youtube.com/watch?v=_V9nnsSwXUM

Posted on Jun 30, 2015 2:26 PM

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Answer 1

BenB

Level 6

12,097 points

Jun 30, 2015 5:38 PM in response to devinbaty

Look at that MIDI region in the Piano Roll editor very closely. I bet there are notes not lining up exactly where they should. I bet their very slightly off enough to do these things.

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Answer 2

devinbaty Author

Level 1

0 points

Jun 30, 2015 6:44 PM in response to BenB

Hey Ben - this definitely isn't an issue of quantizing..the piano roll and the list editor (for the key velocity) display the note starting points, lengths, and velocities as I entered them - clearly things are playing back drastically differently than correctly on the second pass of the playback loop, so obviously the display information and how the events are being realized is radically different at times. That said, since the playback changes depending on both the length of the loop and how many times the loop has been repeated (again, a playback loop, and not a looped MIDI region) I have to feel as though the very same MIDI data is being interpreted in varying though predictable ways (I have no idea how one could accomplish this if they wanted to) - I can open the project on a second computer, and the issue can be immediately reproduced.

In many ways the issue seems tied to measures 33-36 - if I delete the region that covers those four bars and recreate it in an entirely new project where it plays perfectly, then copy and paste it into the gap created by deleting the troubled region, the issue immediately returns even if I delete all automation with the original region. However, if I shift all of the MIDI regions on the track the issue moves the same number of bars in the same direction as the shift, and bars 33-36 will then playback correctly (of course, bars 33-36 will then be a different progression and possibly include a melody line).

While this issue has cropped up twice in two days in two different projects, thankfully they've both been in simple and repetitive projects...I'm incredibly nervous that the problem may appear in a through-composed song with no way to salvage any part of the track in question - it seems as though even if I only copy and paste parts of the track that playback correctly, if I then fill in the sections that don't in a new track or new project, the issue comes back.

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