Friday, March 27, 2020

Polymeter 0.0.28 adds mapping and scales

Polymeter 0.0.28 adds two major new features: mapping, and scales. It also allows step values to be edited numerically, as opposed to by dragging bars in the Velocities pane.

Mapping

The mapping feature supports both translation and mapping to parameters. An input MIDI message can be translated to any other MIDI message, and/or mapped to any track parameter except track name.

An input MIDI message can have multiple mappings, i.e. it can be translated to multiple messages, or mapped to multiple track parameters, or to the same parameter in multiple tracks, or any combination of these. The reverse is also true: different input MIDI messages can be translated to the same output message, or mapped to the same track parameter.

Translation facilitates tweaking synthesizer parameters with a control surface. It’s likely that different songs will use different synthesizers and different modulation schemes. By setting up appropriate translations in Polymeter, the user can avoid reprogramming the control surface for each song. The control surface can always output the same messages; only the mappings need to change, and the mapping details are conveniently stored in the song’s Polymeter document. More importantly, since Polymeter can record the MIDI input as well as the dubs, a performance can be recorded as events and then completely reconstructed afterwards.

Mapping to track parameters is particularly interesting for parameters that affect the rhythmic feel, such as Offset and Swing. The Range Start parameter is another fruitful target. For some track parameters, the mapping’s range may need to be adjusted for optimal results; see below.

Mapping is managed from the new Mapping dockable bar, displayed via View/Docking Windows/Mapping. Mappings can be inserted, deleted, copied, cut, pasted, and reordered via dragging. Mappings can also be sorted by left-clicking the appropriate item in the column header.

The mappings are displayed in a grid control, similar to the track view. Mappings are selected by left-clicking in the # column. Multiple mappings can be selected with Ctrl+click or Shift+click as usual. To edit a mapping property, left-click it. Depending on the column, either a drop list or an edit box is displayed. To set a value in multiple mappings at once, select multiple mappings, and then edit the desired property within one of them.

Each mapping consists of input and output event properties, a data range, and a track selection. The input properties include the input event type (note on, control, etc.), the input MIDI channel, and the note or control number if appropriate. These properties can entered manually, or learned from the MIDI input (see below).

The output properties start with the output event type, which may be either a MIDI message (note on, control, etc.) or a track property. If the output event is a MIDI message, the mapping is a translation, in which case the output MIDI channel and the note/control number are also relevant. Otherwise, the mapping targets a track property, in which case the MIDI channel and note/control number don’t matter, but the track selection is required.

To map a MIDI message to the same parameter in multiple tracks, create multiple mappings, one for each target track. It’s easiest to do this via copy and paste: create a mapping for one of the tracks first, and when it’s set up correctly, clone it as many times as needed, and finally edit the copies to target different tracks.

The range parameters (start value and end value) allow the input MIDI data to be shifted or scaled to any integer range. If the start is bigger than end, the control direction is reversed, in which case turning the knob up makes the value smaller.

The app also supports MIDI "learn" mode, i.e. the input messages can be learned from the MIDI input device. To do this, select a mapping in the Mapping bar, and then enable learn mode via Tools/MIDI Learn, or via the keyboard shortcut Ctrl+Shift+M, or via the Mapping bar’s context menu. The background color of the selected mapping changes to green, indicating that this mapping will be learned. Now twiddle the intended knob on the MIDI input device, and the mapping’s input properties will snap to the appropriate values for that knob. To learn other mappings, select them one at a time and twiddle their intended knobs. After all mappings have been learned, disable MIDI learn mode.

Scales

The scales feature consists of three interrelated modulation types: Scale, Index, and Voicing. The primary purpose of scale modulation is to decouple pitch selection from rhythm. The rhythm comes from the target track’s steps, the pitch set comes from the scale and voicing modulation, and the pitch ordering comes from the index modulation.

When a track has one or more scale modulators, the track doesn’t get its note in the usual way. Instead, it creates a dynamic scale, consisting of the current step values of each of the scale modulators. But which scale tone is used? This determined by index modulation.

Index modulation selects one of the tones in the current scale. A track that uses a scale should also have at least one index modulator. If it has multiple index modulators, they’re summed. The resulting value is interpreted as a zero-origin index into the scale. If the index exceeds the number of scale tones in either direction, it’s wrapped around as needed.

For example, suppose the target track has four scale modulators, and their current steps contain 0, 4, 7, and 11 respectively. This constitutes a Cmaj7 chord. If the target track’s index modulator outputs 0, the first scale tone (C in this case) is selected; if it outputs 1, the second scale tone (E in this case) is selected, and so on.

The range track parameter also works differently in this case. The range if any is applied to the entire scale BEFORE the indexing operation, i.e. before the scale tone is selected.

The target track can still be note modulated. In this case the note shift is added to all of the scale tones, before range modulation and indexing.

Scale modulators can also have note modulators. These are applied first as the dynamic scale is being built.

Voicing

The scale can also be sorted and optionally converted into a drop voicing, by applying one or more voicing modulators to the target track. The voicing modulator’s steps are interpreted as follows: If the step value is one or more, it selects a scale tone to be shifted down an octave (dropped). The numbering scheme is one-origin and starts from the highest-pitched scale tone, i.e. a value of 1 drops the highest scale tone, a value of 2 drops the second-highest scale tone, and so on, as shown below:

0 or below: The scale is sorted, but no voices are dropped.
1: The highest scale tone is shifted down an octave.
2: The second-highest scale tone is shifted down an octave.
3: The third-highest scale tone is shifted down an octave.
And so on. If a voicing modulator exceeds the number of tones in the scale, it’s ignored.

Multiple voices can be dropped by applying multiple voicing modulators to the track. For example, to create a drop 2/4 voicing, apply two voicing modulators, one outputting 2 and the other outputting 4. Many other combinations are possible.

After any voice drops are applied, the scale tones are sorted again, and only then is a scale tone selected, based on the current index modulation.

Step Values

The Step Values bar lets you edit step values numerically, using a grid view. In some case this may be more convenient than dragging velocity bars in the Velocities pane. It’s particularly useful for editing note modulator tracks and similar cases.

To show or hide the Step Values bar, use View/Docking Windows/Step Values. Step values are shown for the selected tracks only. Note that selecting a large number of tracks at once may cause the Step Values bar to perform poorly. It’s recommended that the Step Values bar be hidden when it’s not needed.

To edit a step, left-click it, edit the value or type a new one, and then press one of the following keys:

Enter: Saves the edit. Escape: Discards the edit. Tab: Saves the edit and moves to the next column. Shift+Tab: Saves the edit and moves to the previous column. Ctrl+Down: Saves the edit and moves to the next row. Ctrl+Up: Saves the edit and moves to the previous row.

Various display formats can be selected using the bar’s context menu. If Signed is enabled, the steps are interpreted as signed values from −64 to +64, otherwise they’re considered unsigned values. If Notes is enabled, the steps are displayed as notes, with or without octave information, depending on whether Octaves is enabled. If Ties is enabled, the tie bit (the MSB) is included, otherwise it’s masked off; this is an advanced feature, as is Hexadecimal display.

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