Transcribing, Beat Detection & Variable Tempos

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DPINCGK
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Transcribing, Beat Detection & Variable Tempos

Post by DPINCGK »

I was asked recently to transcribe some old jazz tunes. Several source tracks had tempo changes and rubato sections. I wanted to put each reference track into a sequence where I could align the measure starts and beats in the sequence with the track and then just play along, record MIDI against the track.

The beat detection engine worked on some measures but on many measures - especially the softer sections the beats were not identified correctly. As I was correcting the beat markers in the waveform overview, adding new markers in and deleting others I had wished for a way to just tap along with the track and then slide the recorded taps left or right against the waveform view.

Has anyone else done this and how did you accomplish it?

The solution I ended up with was that I dropped the source audio file into an audio track starting at measure 3, default tempo. Then I made a new MIDI track and just recorded a C3 key into that track for each beat as I listened to the source track. I aligned the MIDI note against the waveform in the Sequence view. When I was done I used DP's inter application MIDI command to send the MIDI output of that track back to DP's MIDI input. I then used the Record Beats command to make a tempo map with that MIDI track as input. It worked fine, and was relatively easy to do but I was just wondering if there was a better / faster way.

Thanks in advance
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bayswater
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Re: Transcribing, Beat Detection & Variable Tempos

Post by bayswater »

I usually end up doing the way you did it. For music with a well defined tempo with simple variations, the tempo detection in DP works fine. But otherwise, you need to do most of it yourself. I've tried this with several other DAWs and dedicated apps, and they're all about the same. One mistake I usually make is to go for more precision than is really needed to get a musically useful map.

If you have to do a lot of this, you might look for some free or cheap dedicated tempo mapping apps. Oddly, there were a couple did a great job on one or pieces, but were useless on anything else.
2018 Mini i7 32G 10.14.6, DP 11.3, Mixbus 9, Logic 10.5, Scarlett 18i8
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FMiguelez
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Re: Transcribing, Beat Detection & Variable Tempos

Post by FMiguelez »

DPINCGK wrote: The solution I ended up with was that I dropped the source audio file into an audio track starting at measure 3, default tempo. Then I made a new MIDI track and just recorded a C3 key into that track for each beat as I listened to the source track. I aligned the MIDI note against the waveform in the Sequence view. When I was done I used DP's inter application MIDI command to send the MIDI output of that track back to DP's MIDI input. I then used the Record Beats command to make a tempo map with that MIDI track as input. It worked fine, and was relatively easy to do but I was just wondering if there was a better / faster way.
I was going to suggest something similar, but your method seems even nicer than mine, since it does not even require a MIDI hardware loop.
I'll have to find out how to do it with software as you described.

So, Inter-application MIDI, huh? Thanks! 8)
Mac Mini Server i7 2.66 GHs/16 GB RAM / OSX 10.14 / DP 9.52
Tascam DM-24, MOTU Track 16, all Spectrasonics' stuff,
Vienna Instruments SUPER PACKAGE, Waves Mercury, slaved iMac and Mac Minis running VEP 7, etc.

---------------------------

"In physics the truth is rarely perfectly clear, and that is certainly universally the case in human affairs. Hence, what is not surrounded by uncertainty cannot be the truth." ― Richard Feynman
DPINCGK
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Re: Transcribing, Beat Detection & Variable Tempos

Post by DPINCGK »

There's a free 3rd party Mac application "MIDI PatchBay". I think I have a patch set up in there to go from DP's inter application DP Output to DP Input but I'm not 100% sure it's necessary or if the process can be done without that utility.
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FMiguelez
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Re: Transcribing, Beat Detection & Variable Tempos

Post by FMiguelez »

Well, I just tried this workflow in a real-life scenario, and I must say it works spectacularly well!

Setting it up is stupid easy>
-- Without me having the slightest idea what I was doing, I simply enabled the IAC bus in the AudioMIDI app by clicking on its "Device is Online" checkbox (so DP sees this published destination).
-- Play the sequence and record playing your taps on a MIDI channel following the tempo as you want the in-progress tempo map to be.
-- Then, I simply reassign this MIDI track's output to an IAC bus. Invoke Record Beats and voila... sit back and watch DP faithfully get your tempo map based on your recorded taps.

-- Fine tune as/if needed with Adjust Beats.

:unicorn:

The advantage of doing it like this, instead of simply actually doing the normal Record Beats workflow, is that it is MUCH easier to do it in sections, or stop and correct something, punch-in, quickly editing after-the-fact, etc.

This resulting tempo map often doesn't even need to be retouched with Adjust Beats.
Oh, and it definitely trumps my (now former) method of doing the MIDI loop with hardware.

So this is an AWESOME undocumented feature that greatly enhances and improves the Record Beats feature to create fluctuating tempo maps.

I LOVE DP :love:
:unicorn:
Mac Mini Server i7 2.66 GHs/16 GB RAM / OSX 10.14 / DP 9.52
Tascam DM-24, MOTU Track 16, all Spectrasonics' stuff,
Vienna Instruments SUPER PACKAGE, Waves Mercury, slaved iMac and Mac Minis running VEP 7, etc.

---------------------------

"In physics the truth is rarely perfectly clear, and that is certainly universally the case in human affairs. Hence, what is not surrounded by uncertainty cannot be the truth." ― Richard Feynman
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FMiguelez
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Re: Transcribing, Beat Detection & Variable Tempos

Post by FMiguelez »

After further use, I discovered that the IAC bus is not really precise... Its timing discrepancies vary anywhere from 450 to 600 samples (around 12 ticks at 120 BPM).

I checked this by comparing the note timings against the actual recorded tempo event after Record Beats from the tapping. There is always that little irregular timing variance.
But compensating for this is quite easy> Simply shift your recorded notes earlier by that amount (since the timing varies a little, they will never sound tick-perfect).

I forgot to mention that, for this to work, the IAC MIDI track must be play-enabled only and NOT record-enabled (DP will give you a Loop error message if you do). You must record enable any other MIDI track to record and "monitor" your playing, then drag the resulting notes to the prepared IAC MIDI track. The tapping sound will be whatever is assigned to the record-enabled track. The flaming between these 2 tracks (between the recorded tap performance in a regular MIDI track and the duplicated/dragged notes to the IAC track) can be corrected as I mentioned above (and this is one of the ways I discovered the mentioned IAC bus irregular latency).
Mac Mini Server i7 2.66 GHs/16 GB RAM / OSX 10.14 / DP 9.52
Tascam DM-24, MOTU Track 16, all Spectrasonics' stuff,
Vienna Instruments SUPER PACKAGE, Waves Mercury, slaved iMac and Mac Minis running VEP 7, etc.

---------------------------

"In physics the truth is rarely perfectly clear, and that is certainly universally the case in human affairs. Hence, what is not surrounded by uncertainty cannot be the truth." ― Richard Feynman
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