How do we embed tempo and slice/transient/stretch markers into a rendered out audio file from Reaper.
It is done in the Render Dialogue where there are several options:
Note – when working in Reaper you cannot embed a Root Key, as it has no project key option. You can embed a key using Acid Pro.
Option 1: Render as WAV file only
No other options selected – no embed tempo or stretch markers. When you bring this file back into Reaper it will load straight onto a track and will not try to conform to the project tempo. Looking at the info for this imported file you can see it has no tempo or slice information.
However if you then subsequently change the project tempo, it will affect the play back speed of the loop if you have your timebase items set to Beats (position, length, rate) as opposed to Time in Project Settings. If you dont want this behaviour set it to Beats (position only)
Option 2: Render as WAV with embedded tempo. Tick the ‘Embed Tempo’ option and render. When you import this file back into Reaper you will be given the option to let Reaper adjust your file to the project tempo or ignore it. (This import option displays according to your Preferences in Media/Import)
When you look at the info for this imported file you can see it now has a heading called: ACID with the BPM of 110.
Option 3: Render as WAV with stretch markers (seems to embed tempo whether selected or not)
To do this you need to add some stretch markers or transient guides to the item in Reaper. That’s a separate topic for another day.
You can only render with stretch markers with the ‘Source’ set to ‘Selected Media Items’ selected in the Render dialogue window.
Now when you import your file back into Reaper you will have more options in the Import Media Dialogue. First of all the dialogue is now called: ‘Slice Import” and there are 4 options:
And when we look at the info for the imported file, it now has slice information as well as BPM.
It’s worth knowing that whether you add transient guides or stretch markers to your item in media and then render – when you import that file back into Reaper and choose to import the file with transient markers, they will appear on the item as green transient guides not stretch markers. As soon as you touch or move one of them they will become stretch markers.
Question is, does having this embedded information help with how flexible you can be moving away from the original tempo and key. I used to find that loops made in Acid Pro and called Acidised loops could take more stretching before unacceptable artifacts crept into the sound, but maybe not so much these days. The main difference I can see is that Acidized Loops contain extra information: not just the tempo and number of slices but the number of beats and the root key.
However with the time stretching algorithms in most DAWs, it’s quite easy to manipulate basic WAV files.
I’m not sure whether to carry on Acidising the WAV versions of my loop collections or just offer WAVS with embedded tempo and maybe slices and Apple Loops. The important thing would be to always include the BPM and Root key in the file name.
