live-sequencer: Live coding of MIDI music
An editor shows a textual description of music (like Haskore), an interpreter computes and emits a stream of MIDI events, and (that's the main point) the user can change the program on the fly. Additionally the state of the interpreter is shown in the form of the current reduced term for educational and debugging purposes.
example usage *****
The live-sequencer does not make music itself, its entire task is to control other software or hardware synthesizers. That is, in order to hear something you need a working MIDI synthesizer such as the sampling based software synthesizer TiMidity. You may run TiMidity and the live-sequencer this way:
timidity -iA & live-sequencer-gui --connect-to TiMidity Simplesong &
This should give you an ongoing stream of notes.
Then change one of the numbers
that appear in the lines like
qn = 300
and press CTRL-R for "reloading" that module into the interpreter.
This should immediately have an effect,
namely increasing the tempo of the melody.
You may also alter a note name like c 4
to cis 4
, then reload,
then undo the modification and reload, again, after a while.
This is the main idea of changing the song while it is playing.
The way the changes are applied warrants
that the change takes effect when the time comes.
Music is not interrupted and
does not need to be restarted for reacting to changes.
The overall task performed by the sequencer
is to lazily evaluate a term called main
that is a list of events.
The value of main
is a stream of midi events
(On/Off pitch velocity
, PgmChange
, Controller
)
or (Wait milliseconds
).
You may wrap a MIDI event in a Channel
constructor
in order to assign the event to the particular MIDI channel.
If you omit this constructor then the event is put to channel 0.
In each step, the head of the main
stream gets reduced
to head normal form (with :
at the top),
and the first arg of the :
gets fully expanded
and it must be a MIDI event.
input language *****
The used language is syntactically almost a subset of Haskell with only strict pattern matching and pattern matching only at the definition level (no case), no local bindings (no lambda, let, where), no types (no type inference, type signatures and type declarations are skipped), and with diet syntax (i.e. drastically reduced syntactic sugar, like no layout rule, no do syntax, no list comprehension, no operator sections).
Semantics is similar to lazy evaluation, but we have no sharing. The design goal is that code can be changed while the program is running. This implies that evaluation of one expression may give different results at different times (e.g., during a live performance, one changes some chords of a musical theme). In turn, this implies that we do not store and share results of evaluations, hence, we don't have local bindings.
You may import and use
the special functions Controls.checkBox
, Controls.slider
from the Controls module.
For every call to these functions a widget is added to the control window
and the state of the widget is the result of the function call.
Technically every change of these widgets
internally adds or updates a rule in the Controls module.
The effect is very similar to updating a value definition in a module
and then reloading that module to the interpreter,
but using the widgets is more intuitive.
Offline rendering *****
In the library interface of this package we provide the basic Live-Sequencer modules in order to allow offline rendering of music that you programmed within the Live-Sequencer. You may generate a standard MIDI file using functions from the Render module. To this end load your song module into GHCi and call
YourModule> Render.writeStream "yoursong.mid" yourSong
HTTP access *****
You may open a browser and view all modules under http://localhost:8080/. If the user of the GUI inserts comments like this one:
----------------
, then it is possible to modify the content below this mark via HTTP. This way multiple people can participate in the composition process. The recommended situation is a room with a data projector and a loudspeaker, where the conductor explains the functions to the auditory and the participants can watch the screen and listen to the music.
You may choose any other port using the command line option --http-port
.
If you want to use a system port like the standard HTTP port 80,
we recommend to configure a firewall to redirect the external port 80
to the internal user port.
We discourage from starting the live-sequencer as root user.
You may disable the HTTP server altogether
by compiling with cabal install -f-httpServer
.
Execution modes *****
There are three modes of execution
that you can choose from the Execution
menu:
Real-time: This is the mode for musical live performances. The interpreter waits according to the
Wait
elements in the main list.Slow motion: This mode is for demonstration and debugging. You can alter the speed using
CTRL-<
andCTRL->
.Single step: This mode is for demonstration, debugging and as a pause mode, when the interpreter reaches the end of the main list. You can trigger evaluation of the next element using
CTRL-N
. Unfortunately it is currently not possible to undo a step.
Editing *****
You can change a module name by altering the module identifier
between the module
and where
keywords
and then triggering module reload.
The same way you can load new modules
by adding import lines and reloading the module.
Alternatively, you may create new modules or close old ones
using functions from the File
menu.
For composition it is useful to play parts of the music.
You can do this by simply placing the cursor within an identifier
or by marking an expression
and then call Play term
from the Execution
menu.
This will make the marked expression the current term
and start playing.
Once the music is playing you can change it
by altering the module and reload it.
However you may find out
that you cannot do a certain modification this way.
In this case you can mark an expression
that denotes a stream transformation function
and call the Apply term
menu item.
This will apply the marked function to the current term.
Useful functions are:
merge newTrack
for adding a new track simultaneously. However, mind the latency!flip append newTrack
for appending some events to the current music.dropTime time
for skipping a part of the music. However this may skip someOff
events and this yields hanging tones. Additionally you may exceed the number of maximally allowed reductions.skipTime time
for skipping a part of the music. This one only removes or shortensWait
constructors. Thus all events are played but you risk exceeding the limit for playing many events at once.compressTime acceleration time
for accelerating the music for a certain time. This should circumvent the problems ofdropTime
andskipTime
.
Limits *****
Without some safety belts it would be very easy to consume all memory or all processing power by accident or by people who contribute malicious code via HTTP. Thus we have added some limits. These have reasonable default values but you can adjust them to your needs via command line options at startup. These are the limits you can set:
maximum number of reduction steps per list element: With this limit you can prevent infinite loops.
term size: With this limit you can prevent memory leaks.
term depth: With this limit you can prevent unbalanced expression trees. Unbalanced trees do not consume more memory than balanced ones, but they consume considerably more graphical space on pretty-printing.
maximum number of events per time period: If your song is too fast or does not contain any
Wait
elements at all, your machine will run out of processing power. Thus you can restrict the number of events generated in a certain period of time. It is controlled by two options:--event-period
sets the time period in milliseconds whereas--max-events-per-period
sets the maximum number of events within this time period. In principle you can consider this a ratio but you cannot simply cancel it. E.g. both--event-period=100 --max-events-per-period=15
and--event-period=1000 --max-events-per-period=150
describe the same ratio, the difference is how liberal is the sequencer with respect to exceeding the ratio for a short time. Read the first setting as: "For 15 adjacent events, the duration between the first and the last one must be at least 100ms." That is, if you emit 20 events simultaneously every second, then the first setting will forbid this, and the second setting will allow it. Thus we recommend to first set--max-events-per-period
to the number of events that you want to emit simultaneously and then set--event-period
large enough to match the power of your machine.
ALSA
Using the --new-out-port
option
you may add more ALSA MIDI ports.
Every port extends the range of MIDI channels by 16 new logical channels.
That is Channel 40 ev
sends an event
to MIDI channel 8 at the second newly added ALSA port
(because 40 = 2*16+8).
Every --connect-to
option refers to the latest added port.
Example:
live-sequencer --connect-to Synth0 --new-out-port out1 --connect-to Synth1 --new-out-port out2 --connect-to Synth2
You do not need to connect to any synthesizer at startup.
You may connect or disconnect the live-sequencer
to any synthesizer once it is running
using aconnect
(command line) or
kaconnect
, alsa-patch-bay
, patchage
(graphical interfaces).
Modules
- Bool
- Chords
- Controls
- Drum
- Function
- Instrument
- Integer
- ListLive
- Midi
- Music
- Pitch
- Render
- Tuple
Flags
Automatic Flags
Name | Description | Default |
---|---|---|
gui | Build the wxWidgets GUI for the sequencer | Enabled |
mplayer | Build the remote controller to the mplayer | Enabled |
httpserver | Enable access to modules via a web browser | Enabled |
Use -f <flag> to enable a flag, or -f -<flag> to disable that flag. More info
Downloads
- live-sequencer-0.0.3.1.tar.gz [browse] (Cabal source package)
- Package description (as included in the package)
Maintainer's Corner
For package maintainers and hackage trustees
Candidates
Versions [RSS] | 0.0, 0.0.1, 0.0.2, 0.0.3, 0.0.3.1, 0.0.4, 0.0.5, 0.0.5.1, 0.0.5.2, 0.0.6, 0.0.6.1, 0.0.6.2, 0.0.6.3 |
---|---|
Dependencies | alsa-core (>=0.5 && <0.6), alsa-seq (>=0.6 && <0.7), base (>=4.2 && <5), cgi (>=3001.1 && <3001.2), concurrent-split (>=0.0 && <0.1), containers (>=0.3 && <0.5), data-accessor (>=0.2.1 && <0.3), data-accessor-transformers (>=0.2.1 && <0.3), directory (>=1.0 && <1.2), event-list (>=0.0.11 && <0.2), explicit-exception (>=0.1.5 && <0.2), filepath (>=1.1 && <1.4), html (>=1.0 && <1.1), httpd-shed (>=0.4 && <0.5), midi (>=0.2 && <0.3), midi-alsa (>=0.2 && <0.3), network (>=2.3 && <2.4), non-negative (>=0.0.6 && <0.2), parsec (>=2.1 && <3.2), pretty (>=1.0 && <1.2), process (>=1.0 && <1.2), stm (>=2.2 && <2.4), stm-split (>=0.0 && <0.1), strict (>=0.3.2 && <0.4), transformers (>=0.2.2 && <0.4), unix (>=2.4 && <2.6), utility-ht (>=0.0.8 && <0.1), wx (>=0.12.1 && <0.14), wxcore (>=0.12.1 && <0.14) [details] |
License | LicenseRef-GPL |
Author | Henning Thielemann and Johannes Waldmann |
Maintainer | Johannes Waldmann <waldmann@imn.htwk-leipzig.de>, Henning Thielemann <haskell@henning-thielemann.de> |
Category | Sound, Music, GUI |
Home page | http://www.haskell.org/haskellwiki/Live-Sequencer |
Source repo | head: git clone git://dfa.imn.htwk-leipzig.de/srv/git/seq/ this: git clone http://code.haskell.org/~thielema/livesequencer/(tag 0.0.3.1) |
Uploaded | by HenningThielemann at 2012-04-15T19:26:13Z |
Distributions | |
Reverse Dependencies | 1 direct, 0 indirect [details] |
Executables | live-mplayer-control, live-sequencer-gui, live-sequencer |
Downloads | 8413 total (32 in the last 30 days) |
Rating | (no votes yet) [estimated by Bayesian average] |
Your Rating | |
Status | Docs not available [build log] All reported builds failed as of 2016-12-25 [all 6 reports] |