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Logic Pro 301
Smart Tempo Demystified
by: joealbano
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  • frankenstrudel
    Posts: 16
    Joined: Jun 24th, 2019
    Logic X Smart Tempo not following audio signal of imported bounce from Logic X
    I've got a song that's 128 BPM until the last verse. At that point it slows to about 100 BPM for ten measures or so and then speeds back up. It's an organic feel, so I recorded the slow-down section naturally without a click and then spliced that recording back into the 128 BPM file at the right measure. In order to use Smart Tempo to map the tempo change, I bounced the whole song to an MP3 and then imported that bounce into a new file with "Adapt tempo" set in Smart Tempo under Project Settings. To be sure the tempo was easy to read, I had added a simple drum track (Boom CHAK! Boom Boom CHAK!) for the whole song, quantized for the first verses, but, of course, left unaltered for the rest of the song. I bounced that song to MP3 and dragged the MP3 into the new file. Smart Tempo analyzed it, but, to my surprise, it arrived at a perfect 128 BPM for the whole song. So, on the one hand, it clearly read "something," but it couldn't have been reading the audio since the tempo change was huge and incredibly obvious. I had even made the drum track extra loud in the mix. It struck me that Smart Tempo had to be reading the BPM setting from the previous Logic file, which must have been burned into the MP3, regardless of the tempo of the actual audio. So I right-clicked on the track and removed its tempo and then copied-and-pasted that tempo-stripped track into another file with Smart Tempo set to ADAPT, but that made not difference. Still 128 BPM for the whole song. So I took the MP3 file to another computer and converted it to WAV format, but this made no difference either. Somehow 128 BPM was still printed into the file itself, without the audio actually being 128 BPM except for in the first verses. 1) Is there an easier way I should have gone about this? and 2) Why in the world didn't this work? If I import a file recorded on another device into Logic set to ADAPT, Smart Tempo does indeed map the tempo fluctuations for the recording.
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  • Joe A
    Posts: 1380
    Joined: Oct 1st, 2013
    Re: Logic X Smart Tempo not following audio signal of imported bounce from Logic X
    Hi Frank - I ran some tests, and Logic did seem to be refusing to strip out or ignore the Tempo information in files I created in or exported from Logic. Even when it asked if it should ignore the embedded tempo and I said yes, it still read it; and even after I stripped out the embedded tempo [as you did -- supposedly not undo-able] and then imported that file into a different Logic session, it still detected the original embedded tempo. Bug or limitation in implementation..? I created a file similar to yours -- drums with a steady tempo, then a slower section [around 20bpm slower], then back to the original tempo. When I did try to strip out the embedded tempo and re-analyze, I got inconsistent results -- it always came back with a single consistent tempo, sometimes picking up the original tempo, sometimes picking up the slower tempo..?!? Tempo detection did work fine when I imported a few files originally created elsewhere. However, when I recreated the same tempo-change drum file in Pro Tools [regular tempo, then slower tempo, then back to regular tempo] and imported it into Logic, while it did analyze it and detect that there was a tempo change at the correct spot in the song, it got the tempo all wrong from that point on [despite the obvious and consistent slower tempo in that section]. So it appears that while Smart Tempo can be very smart when confronted with the kind of small tempo changes typical of a live performance, it may not be so smart when hit with a more substantial or sudden/unexpected change in tempo, where it apparently can easily be flummoxed. [And the fact that you're working with a complete song arrangement probably makes it even more likely that there'd be problems]. I guess you may ultimately have to manually beatmap the tempo-change section to get it right. I always warn people not to expect completely consistent results with this kind of technology -- from any DAW. It's amazing it works as well as it does, but there are always limitations. I have a friend who uses Smart Tempo all the time, always expecting it to work no matter what he throws at it, and he's always running into this kind of unpredictable problem. But it's the same with all these new technologies -- tempo detection, time-shifting, pitch-shifting -- if you use them enough eventually you're bound to bump up against their limits..
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  • frankenstrudel
    Posts: 16
    Joined: Jun 24th, 2019
    Re: Logic X Smart Tempo not following audio signal of imported bounce from Logic X
    Joe, thanks so much for your help, literally recreating the situation on your end. Very much appreciated. I don't know what happened. I replied to your reply that same evening or the next day, but it seems to have disappeared. I was logging on today hoping that you'd replied to that. I wonder if you could give me a quick pointer regarding how to map the beats of the transition manually. Perhaps there is a MPV tutorial specifically about this? I've watched several videos in a course on FlexTime, but I'm not sure they address this kind of issue. It's more about locking into the grid. Would really appreciate a video reference and the right vocab (using the vocab to do the right searches). My experience with tempo changes is limited. I've created tempo changes up in the marker area -- before recording any of the music -- but I haven't started from a recording and worked backwards in order to creating the tempo grid from it. Again, this is a project that slows down for the last verse and then speeds back up. While it's possible to specify those changes beforehand, I at least want to be able to work from an "organically" recorded track (no click), and "read" the desired tempo changes directly from the transients I see. My understanding is that this is possible working from an audio track. A thought I had about a more exact method would be to tap along to all of the beats in a MIDI track, and then map the tracks tempo grid from that MIDI track. And yet, since it's MIDI, it wouldn't have "transients" and such (although I could bounce the MIDI track to audio and then import that track and beat map it?). Is it possible directly from a MIDI track? Thanks so much again for your help. My apologies that the thank-you is so late in coming! Don't know what happened to my previous note. Frank
    Reply
  • Joe A
    Posts: 1380
    Joined: Oct 1st, 2013
    Re: Logic X Smart Tempo not following audio signal of imported bounce from Logic X
    Hi Frank - I think the tapping method is still available via the Global Beat Mapping Track, but there are two other way to do it as well.. - You can use the "Adjust Tempo using Region Length and Locators" command - You can drag the barlines in the Global Beat Mapping Track to the correct notes in the audio track being beat mapped -- it's visual and pretty straightforward [see the screenshot below] Video # 3 [History - Tempo Handling in Logic] in the Smart Tempo course linked above shows those two methods briefly, starting at around 2 minutes in; the barline-dragging approach starts at around 3 minutes in.. Also here's an article that describes the different beat mapping options in Logic -- the article is a couple years old but those features still work the same way: https://www.macprovideo.com/article/logic-pro/beat-mapping-in-logic-pro-x?afid=E470KLQ7r9
    Reply
  • frankenstrudel
    Posts: 16
    Joined: Jun 24th, 2019
    Re: Logic X Smart Tempo not following audio signal of imported bounce from Logic X
    Joe, many thanks for this very thorough answer. On it tonight. Great to have the different avenues and the article. Frank
    Reply
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