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Understanding MIDI Concepts in Pro Tools

The AVID Learning Series Pro Tools textbooks provide an understanding of core-level MIDI definitions and then continue to show how to create MIDI- based tracks (either conventional MIDI tracks or Instrument tracks), record to them and ultimately edit and refine the performance data in Pro Tools.

Some brief background: MIDI was here long before digital recording and computer-based DAWs (Digital Audio Workstations). A MIDI controller transmits performance data- pitch (or note number), velocity, duration, volume, sustain, pitch bend, modulation, panning, after touch, program change, and other controller and system exclusive data. MIDI data could be sent through a MIDI cable, which was capable of transmitting up to 16 channels of discrete data. MIDI sequencers would record and store the data, to then be transmitted to different sound modules in order to play back the recorded events with the appropriate sounds.

Pro Tools integrates MIDI sequencer functionality, allowing the recording, editing, and even importing of MIDI data, on MIDI or Instrument tracks. In previous versions of Pro Tools, virtual MIDI instruments would be launched as inserts on Auxiliary (AUX) tracks. MIDI tracks were then created to record MIDI data (by assigning the proper controller as the track’s input), and then transmit this data to the instrument on the AUX track (by assigning the MIDI track’s output to the corresponding instrument and MIDI channel). In Figure 1 below, you will see the virtual instrument Vacuum as an insert on AUX Track 1, with a corresponding MIDI track (MIDI 1) next to it. Notice the MIDI track has the input from a controller in my system named Oxygen 61, which is plugged into the computer through a USB input (a more current MIDI connection). It is notated as “USBOxyg611”, which signifies MIDI Channel 1 from the controller. The output is assigned to the first instance of Vacuum in our session, on MIDI Channel 1- notated as “Vacuum 1-1” in Pro Tools. The input on the AUX track is irrelevant (since the virtual instrument inserted is being triggered by the MIDI track assigned to it), and the output is assigned to the Main Output 1-2, in order to monitor the sound from the insert. In order to preview the sounds from Vacuum, the MIDI track would have to be record-enabled (clicking once on the red button above the Solo (S) and Mute (M) buttons just above the fader) to enable your controller to trigger MIDI notes and other controller information.



Eventually, Pro Tools developed an Instrument track. This is a “merging” of an AUX track and a MIDI track. A virtual instrument is still instantiated as an insert on this track. However, now you have the option of recording MIDI information directly onto the track itself- unlike an AUX track. In Figure 2 below, you will see another virtual instrument- Mini Grand as an insert on the “Inst 1” track. Again, since you are recording MIDI directly onto this track, the input is not assignable, and the output is set to the main output (Output 1-2) in order to monitor the sound of this instrument. In order to hear the sounds from the Mini Grand, the Instrument track would have to be record-enabled (clicking once on the red button above the Solo (S) and Mute (M) buttons just above the fader) to enable your controller to trigger MIDI notes and other controller information.



These are two virtual instruments that come with Pro Tools 11, as well as two other instruments: Boom (an “old skool” beat box) and DB-33 (Hammond organ emulator). I refer to these instruments as “one-shots”, meaning that they are single channel MIDI instruments. So Instrument tracks are perfect for these, since you can only record one channel of MIDI data per instrument. An exception to this rule would be in the case of splitting MIDI “parts” per one instrument. For example, rather than setting up two instances of Mini Grand for separate left and right hand parts, you could just create two MIDI tracks to both trigger the Mini Grand, playing in each part (left/right hands) on these separate MIDI tracks. This way, when you are finished “perfecting” your performance (MIDI editing), you could then record each part to a separate stereo Audio track- one MIDI track at a time. You would set the output of the Instrument (or AUX) track to an open stereo bus, then matching that bus pair as the input to each Audio track. You would record one track at a time, muting out the opposite MIDI track (Shown in Figure 3 below).



In this example, you would be recording the left hand piano part to the Audio track titled “LPnoPrint”. Notice the appropriate Bus assignments as well as the muted MIDI track of the right hand piano part. This “split-track” recording technique could also be used with Boom (or a similar drum machine instrument), in order to have separate Kick, Snare, High Hat, (etc.) MIDI/Audio tracks. This is just one way of achieving MIDI track separation (more on that in future articles).

The next type of virtual instrument available in Pro Tools is known as a Multi-Channel or Multitimbral instrument. These instruments have more than one MIDI channel. One of these instruments that comes with Pro Tools 11 is called Xpand 2 (see Figure 4 below).



Notice there are 4 discreet channels, each with their own MIDI channel and Part (assigned from Preset banks). If MIDI information is recorded on this Instrument track, it can only be played back on one channel of the Xpand2. Therefore, all the channels in this instrument would have to be set to the same MIDI channel (usually Channel 1 as shown) in order for each of them to sound. This technique is referred to as Layering or Stacking sounds. One common example is adding a string sound, synth pad, or even bell sound to a piano part. The one MIDI performance will trigger each sound at the same time, as long as they are set to the same MIDI channel.

The other way to take advantage of this (or any) multitimbral instrument is to create separate MIDI tracks to correspond with each available channel on the instrument. In the case of Xpand2, we can have up to four discreet channels, each with their own separate sound. This set-up appears in Figure 5 below.



Here you can see the 4 individual parts, each with their own MIDI channel and accompanying MIDI track. As mentioned earlier, MIDI information can be recorded on both MIDI and Instrument tracks. But for discreet multitimbral applications, MIDI channels must be used in conjunction with either an Instrument track or an AUX track with your selected virtual instrument as an insert. Once you have recorded and edited your MIDI data, you could then create separate stereo Audio tracks and internally bounce down the 4 parts one at a time (as previously illustrated more simplistically in Figure 3 above).

Structure Free is the other multitimbral instrument that comes with Pro Tools 11. I will show an example of the full instrument (Structure) in Figure 6 below.



The full version of this instrument is capable of up to 8 banks of 16 channels of MIDI- a lot of real estate! So if you have sequenced 4 or more separate MIDI performances and wanted to record them to their own Audio tracks, it could be quite laborious to have to do them one track at a time. Fortunately, in the full version of Structure (as well as most other third party multitimbral instruments), each channel has it’s own assignable output (see above). So with some careful “assigning”, all Audio tracks can be printed in one pass. This is most helpful for longer formats (songs, etc.). So now, you should be well on your way to MIDI greatness!

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