Pro Tools Tutorials - Making Sense of MIDI and Audio Timebases

Published: 03rd June 2011
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Pro Tools enables you to set a timebase for audio and MIDI/Instrument tracks. You can choose either a Ticks timebase, or a Samples timebase. In this Pro Tools tutorial article you'll learn the very basics of what the timebase setting is, and one of the key ways that it influences the behavior of your tracks.

In Pro Tools when you record (or edit) MIDI data the resolution is measured in Ticks.In the same way that digital audio samples are tied to specific sample locations in the Pro Tools timeline, MIDI events, as well as audio regions on tick-based tracks are tied to tick locations in the timeline.

Musical Note Values vs. Ticks

Typically when you're sub-dividing a single bar using musical note values you would divide it into half notes, quarter notes, 16th notes, 32nd notes, 64th notes and any permutation of the different note values that we use in music.

But instead of using musical note values, Pro Tools sub-divides each bar using a resolution called ticks.

Pro Tools exact tick resolution is 960 ticks per quarter note.

So, let's say you record a single MIDI note event somewhere in the first quarter note of a bar of music. That note event would be captured and located at one of the available 960 tick positions that Pro Tools has divided the quarter note into.

Absolute or Relative Positions

Unlike sample positions which are located at absolute points in time, each of the 960 tick locations are located relative to the particular bar and beat locations in the session.

For example, a MIDI note located precisely on the first 8th note of bar X would be at tick position 480 (one half of 960) after the start of bar X. Now (and this is the key thing) if you changed the tempo of the session, that event will still be on the 480th tick position of beat one of bar X and will retain that 480 tick distance from the start of the bar.

KEY POINT: MIDI events on Tick based tracks retain their relative position to other MIDI events, regardless of changes to the tempo.

Increase the tempo and the MIDI events move closer together. As a result they play faster.
Decrease the tempo and the tick positions and the MIDI events on them will move away from each other while retaining their relative position. They'll play back slower.

Now you may be thinking - big deal. MIDI plays back slower if you slow down the tempo and speeds up if you increase the tempo. Don't MIDI tracks always behave that way? And therein is the point of discussing ticks time base: Yes - MIDI tracks do follow tempo. But only when they are set to ticks time base. Not when they are set to samples time base.

Pro Tools enables you to assign MIDI tracks to the ticks time base (the default setting) or to the samples time base. This opens up a whole new way to work. Especially when you consider the fact that either ticks or samples time base can be selected for audio tracks, too. Not just MIDI tracks.

For now the key thing to remember is that tick based tracks follow the sessions tempo.

Tips for learning more about Ticks time base

Use the following steps and try experimenting with Ticks time base in your own Pro Tools system.

First, the setup.

First, create a new session in Pro Tools.
Create an Instrument or MIDI track and record some MIDI data on it. Preferably some note that you can hear playing back.
Also, create an audio track with a few regions of audio on it.

Make note of the session tempo. You'll need to reset it as you do the next steps.

Once you've got those steps completed, try the following.

With the audio track set to the default Samples time base, and the MIDI track set to the default Ticks time base, adjust the session tempo.

Notice that the MIDI events on the MIDI track change as you adjust the tempo. But the audio regions on the audio track do not. They stay in position.

Important: before proceeding, reset the session tempo to the starting tempo.

Next, switch the MIDI track to samples time base, and the audio track to ticks time base.
Now press play and as you're listening, make changes to the tempo.
Notice this time that the MIDI notes do not move but the audio regions do.

Final Notes

For now my hope is that you've gained a clear understanding of the basics of the ticks time base and how it affects the behavior of both MIDI events and audio regions.

Now that you know essentially how the ticks time base affects regions and MIDI events, you'll need to explore how putting it use can help you to create better music, more efficiently.. Keep at it!

About the Author

Chris Bryant is a music producer, pro audio consultant, and educator in Vancouver, Canada.

Learn Pro Tools online at www.pttuts.com - a complete online training library of clear and detailed Pro Tools Video Tutorials and more.



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