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Technically, a Cmd is anything in the Cmd.Cmd.CmdT monad. The Cmd monad is basically just a state monad on Ui.Ui.State and Cmd.Cmd.State, which means a Cmd is a function that can modify the score or the app state.

Bound Cmds are just functions that take a Cmd.Msg.Msg and decide whether or not to do something based on that: Msg.Msg -> Cmd.CmdId Cmd.Status. Most of them are bound in Cmd.GlobalKeymap and track-specific ones are bound from Cmd.Track. The keymap bound cmds are summarized in the keymap doc, and the track commands mostly depend on the EditMode.

However, most Cmds are accessible only from the REPL.


Tracks are indexed by Ui.Types.TrackNum, starting at 0 on the far left. In practice though, the 0th track is usually the ruler, so the “real” tracks start at 1.

A track can be addressed either by a (BlockId, TrackNum) pair, or directly by a TrackId or RulerId. The functions in Ui.Ui enforce that a given TrackId can only appear in a block once, so you can convert between TrackId and TrackNum. The TrackNum is actually more general, in that it may address a ruler or divider, so functions that expect an event track or don’t care where a track is on a block will generally take a TrackId.

The actual meaning of the tracks is defined by derivation, the documentation here is just the low level, without reference to what it means. This is analogous to syntax in a normal language.

There are three kinds of tracks: divider, ruler, and event.

divider track

Ui.Block.Dividers are just visual spacers. All they have is a color and a width. You can add one by hand with Cmd.Repl.LBlock.divide to visually separate tracks, and they are used automatically to represent collapsed tracks.

ruler track

The ruler by convention is in TrackNum 0, which on the far left, and is special in that it stays put and doesn’t scroll right to left like the other tracks. It provides a visual reference for the rhythmic structure and is analogous to the meter. If you are so inclined, you could put an event track in TrackNum 0, perhaps as a reference. Or you could have multiple rulers, which is analogous to multiple simultaneous meters. However, cmds that deal with rulers generally expect only one ruler per block, and that it be in TrackNum 0, so you might have to make those smarter. Cmd.Repl.LRuler does have basic support for multiple meters, in that it can modify a single track, or a group of tracks bound by a ruler track to their left, or all the tracks in a block.

A Ui.Ruler.Ruler has Ui.Ruler.Marklists, which is just a list of Ui.Ruler.Marks.

A ruler can have marks in any kind of arbitrary pattern, but typically you’d want them dividing up time according to a meter or tala or whatever system you use. Cmd.Ruler.Meters has European-style meters, while Cmd.Ruler.Tala has Carnatic talas. Normally you’d use the functions in Cmd.Repl.LRuler to modify the ruler or create new rulers.

While ruler tracks have a ruler only, event tracks have rulers too, which show up as transparent lines. Normally all tracks in a block have the same ruler, but if you want you can set up different meters for different tracks, in the same way you can have multiple ruler tracks.

Since rulers are addressed by RulerId, they have an identity and are shared. So you need to be aware if you are modifying an existing ruler, which will change all blocks with that ruler, or if you are creating a local copy. The Cmd.Repl.LRuler.modify and Cmd.Repl.LRuler.local functions apply a ruler modification destructively or to a local copy, respectively. The LRuler functions should delete rulers when no references remain, but not always, so Cmd.Repl.LRuler.gc will do that explicitly.

event track

Event tracks have Ui.Event.Events. They are divided into several types, differentiated by their titles. Details are in the derivation doc. Since this is the track that holds score data, and which you spend most of your time editing, “track” usually means an event track, not a ruler. Usually I say “note track” or “pitch track” or “control track”, all of which are event tracks at the low level, but are distinguished by their titles and treated differently by cmds and derivation.

Of course, to be visible, a track has to live in a block. The same track, identified by its TrackId, can be in multiple blocks at once, but it can only appear once in each block. This restriction is for convenience, since otherwise just a (BlockId, TrackId) pair wouldn’t be enough to identify a track. Note that when you remove a track from a block, the track still exists, and is accessible via its TrackId. Cmd.Repl.LTrack.gc will delete all tracks that aren’t referenced by any block.

The data inherent to a track is in Ui.Track.Track, and data which may vary per-block is in Ui.Block.Track. The most interesting is a set of Ui.Block.TrackFlags, which affect display, derivation, or performance.

One special case is merged tracks. Since note calls frequently have no text and just mark a start time and duration, and control calls frequently have text but no duration, you can save space by merging the neighbor pitch or control track into the note track. Merging is a purely display feature, where the text from the events in one track will be displayed right-aligned in another track. By convention (i.e. what the default keybindings do), the merged track is the adjacent pitch track, which is then collapsed.

note track

Note tracks actually produce score events. The cmds are implemented and documented in Cmd.NoteTrack.

Because most instruments are pitched, note track cmds listen for pitches (either from the MIDI keyboard or kbd entry) and enter pitches on a neighboring pitch track, or create one if it doesn’t exist. So they mostly act like pitch tracks. But ValEdit on note tracks also supports Cmd.Cmd.state_chord to enter chords easily, and Cmd.Cmd.state_record_velocity.

Instruments can carry their own Cmds, which come into scope on the relative note track. So for instance an drum instrument may override the note track Cmds so that entering notes creates drum strokes rather than pitched notes.

pitch track

Pitch tracks produce a pitch signal, and the cmds are in Cmd.PitchTrack. They’re mostly concerned with turning pitch input into the named pitch for the scale in scope.

control track

Control tracks generate Perform.Signal.Controls, which are numbers that vary in time. The cmds are in Cmd.ControlTrack. By convention they are normalized between 0 and 1. This makes them multiply together nicely, which is convenient, because that in fact is what they do by default. But they are not restricted, and for example a control indicating the amount of delay, or the depth of a trill would have no reason to stay within that range.

But since they mostly are normalized, the default call to set a control value is a bit weird, though it may be familiar if you’ve used a tracker. ValEdit will accept hex “higits” and replace any existing number. The value is superscripted with an x to indicate that it’s in hex, and is divided by 0xff to normalize it. This makes it fast and convenient to type normalized numbers, makes them all the same physical width, and doesn’t rely on a tiny decimal point to determine their magnitude. But you can still use floating input enter decimal numbers if you like them, or need numbers outside the 0–1 range. As documented in Cmd.ControlTrack.cmd_val_edit, a track is only edited in normalized mode if it’s inferred to be normalized.

tempo track

Tempo tracks, also implemented in Cmd.ControlTrack, are in most respects normal control tracks, except of course they are treated differently by the deriver. They’re not normalized between 0–1, so they don’t do the hex input thing.

Signal render

Tracks can display a visual representation of a signal, namely the signal which that particular track generates. You have your choice of Ui.Track.RenderConfigs, and it works on pitch tracks too. Note tracks are handled separately, as documented in RenderConfig. Cmds in Cmd.Repl.LTrack turn signal render on and off.


Selections are colored transparent rectangles that are drawn in event or ruler tracks, starting at some time and ending at some other time. At the lowest level, that’s all they are, but of course cmds establish some conventional meanings for them. The most frequently used is the insert selection, which corresponds to the “edit point selection” found in most programs, but there are others, configured and documented in App.Config.insert_selnum.

Selections can have zero duration, at which point they’re called “point selections” and in the case of the insert selection, some cmds may behave slightly differently, e.g. act upon an overlapping or previous event rather than the events strictly contained within. It’s all rather ad-hoc and complicated, but is hopefully what you expect, as long as your expectations are similar to mine.


Besides visual reference, rulers also provide snapping points for the insert selection.

A Cmd.TimeStep.TimeStep describes a time interval, some of which are in terms of ruler mark ranks. Utilities in Cmd.Ruler.RulerUtil can create and modify rulers with appropriately spaced marks, which cause the various timesteps to correspond to whole notes, quarter notes, etc. The short form of a TimeStep as emitted by Cmd.TimeStep.show_time_step uses mnemonics like w, h and q, and in European meters these generally correspond to whole, half, and quarter notes, but not necessarily exactly, as documented in Cmd.Ruler.Meter.


Cmd.Cmd.EditMode is a global mode setting, which is somewhat analogous to vi’s modes. Basically, each mode enables different editing oriented cmds.

The current edit mode is displayed in the edit box, above the ruler. The mapping is in Cmd.Internal.sync_edit_box, but basically a color means you’re in some edit mode, and gray means you’re in command mode.

The precise effect of each edit mode depends on the track:

In ValEdit mode, number keys on a control track will enter numbers. A pitch track will listen for notes, either from a MIDI keyboard or from kbd input, and will create the appropriate pitch. A note track will create a note along with an entry in the pitch track, creating a pitch track if the note track doesn’t already have one.

MethodEdit is for control and pitch tracks. It’s just a way to edit the call of the control or pitch (which is itself a call, but never mind that). For example, you would turn on ValEdit, type a number like 1, then switch to MethodEdit (tab, by default) and type i to wind up with i 1. What that means, of course, is documented in control calls.

floating input

Floating input is technically not a edit mode since it’s not in Cmd.Cmd.EditMode, but it’s used to enter or alter text. For example, the “append text” cmd (bound to ‘a’ by default), brings up a floating text input to edit event text directly.

Events created on control and pitch tracks will normally be zero duration. Events on a note track will use the duration of the current note duration TimeStep, but if you select a range of time and then create an event, the event will be exactly that duration. Additionally, if the text has a leading space, the space will be stripped and the event created with a zero duration.

If you hit escape in any text entry field, it will revert your changes.

note entry

Note entry mode (Cmd.NoteEntry) is actually orthogonal to EditMode, in that it can be enabled and disabled independently, but is conceptually also a mode. It turns the ASCII keyboard into a music keyboard by remapping the keys to emit pitched notes. It’s often more convenient to use a MIDI keyboard, though, because then you get to keep the ASCII keyboard for cmds.

But since the ASCII keyboard is actually analogous to a 10-key per octave keyboard with black keys in between each white key, it can be more convenient for scales with non-piano layouts. This also allows it to behave slightly differently, for example relative scales always start at z and q (the “middle c” of the ASCII keyboard), even for the piano style scales, because the ASCII keyboard allows black keys to be anywhere.

An input note, whether via MIDI or ASCII keyboard, is represented by a Perform.Pitch.Input, which has more information about how they’re represented.

Sometimes I call this “kbd entry”, though I’m trying to standardize on “note entry.” They’re both kind of vague though.


See integration.


Derive.Scale.Scales have a Cmd component, since how to input and modify scale degrees depends on the scale. Each scale has a bunch of ad-hoc functions to support cmds that work generically across all scales, like symbolic transposition or mapping an input key to a scale degree.

There is quite a bit of complication in scales relating to enharmonics, spelling, keys, and the like, much of which is documented in the support modules like Derive.Scale.ChromaticScales and Derive.Scale.Theory. If you want to manipulate pitches in a higher-level way than just an opaque symbol, you’ll need to use the various functions used to construct the scale to parse the degrees and get at their internal structure.

The details of how scale degrees turn into frequencies is handled at the derivation level.


Instruments have some presence at the derivation level, and most of their complication is at the performance level. But they can also bring Cmds into scope, via Cmd.Cmd.inst_cmds. These cmds are only in scope on note tracks, and there are utilities for their definition in Cmd.Instrument.CUtil. Generally they do things like special input keys for drum maps.

Unfortunately, cmds are not yet introspectable for documentation like deriver calls are, so while the Instrument.Browser can reveal their presence, you’ll have to look at the instrument’s source to know what they are.

DAW synchronization

Since Karya doesn’t host VSTs or record audio, you’ll need a DAW to do those things. Apparently the only way to do this is MTC, which sends a continuous stream of SMPTE time frames. Karya can also use MMC to set the play head position. See Cmd.Cmd.state_sync for how to set this up on the Karya end.