11. Editing MPE
MIDI Polyphonic Expression (MPE) is an extension to the MIDI specification that enables attaching parameter control information to individual notes, instead of globally per MIDI channel. This way of using MIDI allows MPE-capable devices to control multiple parameters of every note in real time for more expressive instrumental performances.
To enable Live to receive per-note expression from an MPE-capable MIDI controller, first enable MPE Mode in the Link/Tempo/MIDI Preferences for that controller.
Note that when selecting a MIDI controller that has MPE enabled as an input device on a track, the channel input routing is fixed to “All Channels’’ and no individual channels can be selected.
For more information about working with MIDI controllers, please refer to MIDI and Key Remote Control (see Chapter 29). Once your controller is set up, you can use it to record new MIDI clips (see Chapter 17) containing MPE data.
The Clip View’s Note Expression tab allows viewing and editing five dimensions of MPE for each note in a clip: Pitch (per-note pitch bend), Slide (per-note Y-Axis), Pressure (Poly Aftertouch/MPE Pressure), Velocity and Release Velocity (Note-Off Velocity). This makes it possible to refine the expression of recorded material, or to automate polyphonic sound variations for MPE-capable instruments.
Note that you can view and edit MPE data for notes in all MIDI clips, regardless of whether those clips were created using an MPE-capable device or using other methods (see 10.1). We will look at viewing and editing MPE data in the following sections.
11.1 Viewing MPE Data
To view MPE data in a MIDI clip, first enter Clip View by double-clicking on a clip, then click on the Note Expression Tab or use the key command ALT-3(PC) / ALT-3(Mac) to open the Expression Editors at the bottom of Clip View. Four of the five MPE parameters are contained in their own expression lane: Slide, Pressure, Velocity, and Release Velocity. By default, only Slide and Pressure are shown. Envelopes for the fifth parameter, Pitch, are displayed on top of their corresponding notes in the MIDI Note Editor.
Each expression lane can be shown or hidden via the lane selector toggle buttons at the left. Underneath the lane selector toggle buttons, a triangular toggle button allows showing/hiding all enabled lanes at once.
When all expression lane selectors are hidden/disabled, pressing the triangular toggle button will show all expression lanes at once. Each expression lane can be resized individually via their split lines. All expression lanes can be resized simultaneously by dragging the split line between the lanes and the MIDI Note Editor.
Pressing ALT(PC) / ALT(Mac) and clicking the triangular toggle button displays all expression lanes. When hiding the expression lanes using the triangular toggle button, or by dragging the Expression Editor View split line, the lane visibility toggles are hidden as well.
11.2 Editing MPE Data
When clicking a note (or any of its expression dimensions) in the MIDI Note Editor while the Note Expression tab is open, the note will appear in a transparent overlay. Envelopes appear, along with any existing breakpoints, to allow editing the note’s Pitch, Slide, and Pressure envelopes, while markers can be used to edit the note’s Velocity and Release Velocity values. Unselected notes will appear grayed out, and their expression envelopes will be dimmed.
After clicking on the note or envelope you wish to edit, all expression breakpoints for the chosen envelope and the line segments connecting them become draggable objects. Clicking and dragging in the envelope’s background defines a selection. Here is what you can do:
- Click at a position on a line segment to create a new breakpoint there.
- Click on a breakpoint to delete it.
- To help you edit breakpoints more quickly, expression values are shown when you create, hover over, or drag a breakpoint. Note that when hovering over or dragging a selected line segment, the expression value shown will correspond to the breakpoint value at the cursor’s current position.
- Click and drag a breakpoint to move it to the desired location. If the breakpoint you are dragging is in the current selection, all other breakpoints in the selection will follow the movement.
- Click right-click(PC) / CTRL-click(Mac) on a breakpoint and choose Edit Value from the context menu. This allows you to set an exact value in the editable field using your computer keyboard. If multiple breakpoints are selected, they will all be moved relatively. Similarly, you can also create new breakpoints at an exact value by clicking right-click(PC) / CTRL-click(Mac) on a preview breakpoint and choosing the Add Value command.
- Click near (but not on) a line segment or hold Shift and click directly on a line segment to select it. With the mouse button held down, drag to move the line segment to the desired location. If the line segment you are dragging is in the current time selection, Live will insert breakpoints at the selection’s edges and the entire segment will move together.
- In the Note Expression tab, the grid is disabled by default for easier editing at a finer resolution. Note that the grid’s settings are separate from the grid in the other tabs, and they are saved with the clip.
- If needed, you can enable the grid using the Snap to Grid options menu entry or the CTRL-4(PC) / CMD-4(Mac) shortcut. When the grid is enabled, breakpoints and line segments will snap to time positions where neighboring breakpoints exist. Breakpoints created close to a grid line will automatically snap to that line.
- When moving a line segment or breakpoint, hold Shift while dragging to restrict movement to either the horizontal or vertical axis.
- Holding down the Shift modifier while dragging vertically allows you to adjust the breakpoint or line segment value at a finer resolution.
- You can remove a neighboring breakpoint by continuing to drag a breakpoint or line segment “over” it horizontally.
- Hold ALT(PC) / ALT(Mac) and drag a line segment to curve the segment. Double-click while holding ALT(PC) / ALT(Mac) to return the segment to a straight line.
- Except for the Pitch expression envelope, you can scale Slide, Pressure, Velocity and Release Velocity envelopes proportionally across a note’s entire duration, similar to that of velocities for multiple selected notes. To do, first click outside of the note’s area, then hover the mouse above the desired envelope. When the envelope turns blue, click and drag up or down, and the envelope will be scaled accordingly. This is also the behavior when editing expression envelopes for multiple selected notes at once.
- You can also adjust all selected breakpoints equally, rather than scaling them. To do so, first click on the envelope you wish to edit, then use CTRL-A(PC) / CMD-A(Mac) to select all of the breakpoints, then drag up or down with the mouse as desired to increase or decrease their value; dragging left or right will move all breakpoints horizontally as a group.
- When a note is moved, its expression envelopes will move along with it.
- Pitch breakpoints snap to the nearest semitone when pressing ALT(Win) / CMD(Mac) while the grid is off. This also works for Pitch values in Draw Mode. This behaviour can be bypassed using the same shortcuts when the grid is on.
- Pitch envelopes are hidden when Fold Mode is enabled in the Note Expression tab.
11.3 Drawing Envelopes
With Draw Mode enabled, you can click and drag to free-handedly “draw“ an envelope in the Pitch, Slide and Pressure expression lanes.
To toggle Draw Mode for MPE data, select the Draw Mode Option from the Option menu, click on the Control Bar’s Draw Mode switch, or press B, then click on the envelope you wish to edit. Holding B while editing with the mouse temporarily toggles Draw Mode.
Holding down the Shift modifier while dragging vertically allows you to adjust the expression value of a step at a finer resolution.
When the grid is enabled using the Snap to Grid options menu entry or the CTRL-4(PC) / CMD-4(Mac) shortcut, drawing creates steps as wide as the visible grid, which you can modify using a number of handy shortcuts (see 6.9). To temporarily enable drawing in the grid while it is disabled, hold down ALT(PC) / CMD(Mac) while drawing.
11.4 MPE in Live’s Devices and on Push
The Arpeggiator effect (see 25.1), Sampler instrument (see 26.7) , and Wavetable instrument (see 26.10) all support MPE, and each of these devices has MPE presets that bring new dimensions of interaction and playability to your sound. The expressive possibilities within these devices also enable you to take advantage of polyphonic aftertouch on Push.