TB303 Rack (Beta release)

Overview

The TB303 is a rack of monophonic synths, performing a direct modelling of the classid Roland 303 Bassline. Each synth is associated with its own crude monophonic sequencer, and seperately sends and receives MIDI note and control data. Presently, the sequencers are limited to 16 notes: 4 beats of sixteenths. In other words, this is a snappy little techno groove generator.

Usage

The first 303 to be run creates the main control page, and opens the midi in/out ports (presently this is hard-coded to "midi1", the top pair of ports). Subsequent launches of the 303, up to the hard limit, create a status/control region on the main window specific to the new synth/sequencer pair.

The screen is divided into four areas:

1. The top line displays the name of the "top" 303, the one which is currently being controlled by the sliders and screen knobs. This are will be used for other pices of general usage in later releases.
2. The next three lines give sequencer controls.
   • The "start" button starts and stops the sequencer.
   • The "rand" button generates a random 16 note C-major sequence in the current sequence.
   • The "seqi" buttons load (on a left mouse click) and store (on a right click) sequence data into common storage. This data also includes the tempo, start, and end point settings.
   • The slider controls sequencer tempo.
   • The "trans" text field transposes the current sequence by a given amount (see Bugs below).
   • The start and end points are integer indexes into the sequence.
3. The next 10 or so lines are controls for the synth itself. The sliders are almost self explanatory, and are best understood by playing with them. They roughly correspond to controls on a 303. The "slideri" buttons store (right click) and load (left click) synth settings to and from an area common to the 303 rack.
4. The last region contains controls specific to individual running 303s.
   • The first button sets the selected 303 to be "top" (i.e. under control of the screen sliders and buttons).
   • The "mute" button is not currently operational, but will be so in the next release (you've just got to stop adding features sometime)_.
   • The next two lines give sequencer status ("Active/Paused") and an indication of which area the 303's sequence was loaded from.
   • The next line gives the midi receive channel. Currently understood is noteon, noteoff, and keypress messages, and control data, which is sent to the sliders.
   • The next line gives the midi transmit channel. Currently, only control messages are sent from the sliders. This however can be damned useful.

The relationship between midi control change messages and sliders is:

• B_PAN controls the pan.
• B_MODULATION controls filter resonance.
• B_BREATH_CTRL controls the filter envmod.
• B_GENERAL_CTRL_1 controls the cutoff frequency.
• B_GENERAL_CTRL_2 controls the feedback.
• B_GENERAL_CTRL_3 controls the tempo.
• B_GENERAL_CTRL_4 controls the amplitude slider.
• controller 0x0c controls the delay factor.
• controller 0x0d controls the decay parameter.

Slated for future releases

Known Bugs and Limitations

• There is a bit of lag in the keyboard/external sequencer response. It's not measurable, but more of a feel thing, and probably no worse than that in a lot of old analog gear anyway. This seems to do with the fact that the audio subscriber (as I understand it) doesn't like buffer sizes less than 4k. This is quite a whack of pre- calculation, and I share your concern. (Be: please prove me wrong).
• The default sequence gets very annoying.
• Control change information occasionally gets mangled. This happens somewhere between my keyboard and the BMidi interface, and might not be a problem on other setups.
• The transposition textcontrol does not send a message if the text is not changed. This is a problem with the BControl itself. Changing the field with a space will get around this problem (eck!).
• More than 7 running at once will bring a dual-66 to its knees, requiring a 2 finger reset to alleviate the problem. This is not a problem on the dual-133, but the limitation is presently hard-coded.

Authors

• David Karla (dak@cs.latrobe.edu.au)
• Alistair Riddell (amr@farben.latrobe.edu.au)
• Ross Bencina