]> Git — Sourcephile - tmp/julm/arpeggigon.git/blob - SPEC.md
Edit change log.
[tmp/julm/arpeggigon.git] / SPEC.md
1 Reactogon Design
2 ================
3
4 2016-05-18: INCOMPLETE, but should give an idea. Refine/structure better
5 as see fit.
6
7 Target levels
8 -------------
9 - [ ] Baseline: text interface only, not necessarily (very) interactive,
10 but at the very least able to record a performance as a MIDI file.
11 - [ ] Basic system with a GUI running on a Linux desktop. At least able
12 to generate sound
13 - [ ] Full-featured system with GUI running on a Linux desktop.
14 - [ ] Mobile version, subject to cooperation with Ivan/Keera Studios
15
16 Feature Summary
17 ---------------
18
19 * Modelled after the original Reactogon
20 * Up to 16 layers. Each layer an extended version of the original Reactogon.
21 Extensions include:
22 - Each tile has an associated "repeat count" n. The play head stays
23 on the title for n clock ticks, repeating any basic action for
24 each tick, before moving on (possibly in new direction).
25 Specifically, this means that n = 1 is the normal behaviour and
26 n = 0 means the play head moves on immediately without performing any
27 action.
28 - User-defined "groove" per layer. E.g. every other beat can be delayed for
29 a swing feel.
30 - Accented (more strongly played) notes.
31 - Slide (kind of slide *could* even depend on direction of the play head!)
32 (not going to work well for polymorphic layers probably. But the MIDI
33 translator could simply ignore slide messages until the current one is
34 done. Then everything OK as long as no overlapping slides.)
35 - MIDI CC/program change can be sent for a note
36 - Two tempo-synched LFOs per layer
37 - Bank and Program
38 - Volume slider
39 - Pan pot
40 - Layer transposition
41 - A layer can be set to be unpitched: the pitch of all output notes
42 are set to a specific pitch (useful for e.g. rythm layers).
43 - Muting and Soloing of layers
44 * MIDI integration
45 - synchronization to external MIDI clock if selected and available
46 - start, stop, continue: send and receive
47 - each layer transposed in response to note on message on designated channel
48 - designated MIDI channel for each layer for output:
49 + note on/off
50 + program change
51 + volume
52 + pan
53 + mapping of LFOs to specific MIDI CC (including volume or pan which
54 overrides the static values).
55 + pitch bend
56 * Dynamic addition/deletion of layers(?) Or simply a fixed number of layers?
57 * Overall control/performance tab. For ecach layer:
58 - Volume
59 - Pan
60 - Mute (inhibits all MIDI out messages, but layer continues to run)
61 - Solo (messages from all other layers inhibited, but mute status
62 preserved; only one layer at a time can be soloed)
63 These controls duplicated on each layer
64 * Saving & loading of configurations
65 * Loading of individual layers from stored configurations.
66 * Directly recolrding to/generating a MIDI file. Record button?
67
68 Clocking
69 --------
70 The system beat, relative to which the overall tempo is given (in BPM)
71 is defined to be one quarter note.
72
73 The layer beats is specified separately but defaults to one quarter note.
74
75 A beats per par is also specified per layer. Together with the layer beat
76 this gives the time signature (of sorts) for a layer.
77
78 The system tempo is either set internally, in BPM, or synched to an external
79 MIDI clock.
80
81 Sufficiently flexible swing could be specified per layer by specifying
82 how much earlier or later beats 2, 3 and 4 should be relative to a straight
83 beat, i.e. three numbers between say -90% and 90%. A standard swing
84 beat would thus be given by 50, 0 50.
85
86 Only beat numbers as defined by the layer's beats per bar would be used,
87 and beat numbers beyond 4 would be played straight.
88
89 Or one might want to allow the number of numbers to be beats per bar minus 1.
90
91 Overall Structure
92 -----------------
93 ------------------
94 | |
95 Model <----> GUI <----- |
96 | | |
97 |--> Global-+----->| |
98 | V | V
99 +------> Layers -----> MIDI translator ---> MIDI Synth
100 |
101 MIDI keyboard --
102 |
103 (MIDI clock) ---
104
105 Gloal, Layers, and MIDI translator are all FRP (Yampa) moduled.
106
107 * Global (better name needed!) takes care of system-wide signal
108 processing, e.g. definition of the system clock, run/stop logic?
109
110 * Each Layer is a Reactogon. The core semantics is defined in
111 BasicSemantics. The intention is to lift (most of) this into
112 an event-processing signal fnction using "accumBy". Additional
113 signal functions per layer would be needed to define the
114 layer clock, layer LFOs, and maybe more.
115
116 * The MIDI translator is responsible for translating the collective
117 output from the layers (high-level MIDI notes, LFO output) into
118 low level MIDI events. This involves things like ensuring that a
119 note off event is scheduled for every note on event at the appropriate
120 time, translating and realising continuous control signals
121 (from LFOs, slide ornaments) into discrete MIDI messages,
122 and merging it all into a single sequence of events, taking the
123 limited capacity of a standard MIDI connection into account
124 (more corse grained translation of continous control signals
125 if too busy? dropping notes in case of excessive polyphony per
126 channel and/or overall?)
127
128 * The GUI manipulates a model of the system tailored to the needs of the
129 GUI. Control signals are derived from this for Global and each
130 layer (e.g. the configuration of a board, the board transposition).
131
132 The GUI also needs to observe the output from Global and Layers
133 to animate layers as the play heads move around and to display
134 the system tempo in case this is derived from external MIDI clock.
135
136 The GUI also needs to talk to the MIDI translator to send e.g.
137 configured prgram change, bank, volume and pan messages for each
138 layer whenever the Reactogon is started.
139
140 Muting of layers could also be achived this way by instructing
141 the translator to temporarily stop listening to a muted layer.
142 (Muted layers would still run and be animated.)