The Expresso tool lets you play with an L-systems fractal generator, which takes a simple musical expression (literally the expression "X") and mutates it. In each generation, transformations are applied to components of the expression. The more generations there are, the larger and more complex the expression gets. The output varies wildly, from boring to fascinating.

To generate a new result in the Expresso tool, press the "Gen" button. The default behaviour (as of 10/30/2000) of the Expresso tool is to immediately start playing *and* looping the result. If you don't like this, you can use "More->AutoPlay->Off" to turn off the automatic-playing behaviour, and you can use "More->Loop->Off" to turn off the looping behaviour.

By default, the pitches in the result are not filtered in any way, so the result is fairly random sounding (especially since the default value of X is a single note).

Let's say you want to want to force the pitches to be in a particular scale (or just a particular set of notes). To do this, the easiest way is to use your MIDI input device. First, you must select the "More->AutoApply->Scale all to Last Recorded" menu item. From then on, every time you generate a new result, it will be automatically scaled to the last set of notes that were seen on MIDI input. To try it, press a single note (say, middle C) on your keyboard, and then press "Gen". The new result should consist of only C notes. (Remember, you need to select "More->AutoApply->Scale all to Last Recorded" to enable this mode.)

If you don't have a MIDI input device, it is still possible to set tne scale notes - first you put the desired notes into the Snarf, then use the "More->Load Grab from Snarf" item to put them in the "Grab" area, and then using "AutoApply->Scale all to Grabbed". You can use the "Chord" tool as a convenient way of setting the Snarf value to a chord, for use in this way.

By default, the Expresso result is truncated to 8 beats. You can modify this with the "More->AutoLength" menu. If you set AutoLength to "off", the length of the result will vary (and will be longer if the number of generations is higher).

The default number of generations is 9. The button that controls this is right below the "More" button - there is a "g" next to the button, "g" stands for "generations". The more generations you do, the more complex the results will be.

You can vary the overall pitch of the result by using the button next to the "o" ("o" for octave). If you set the "o" value to "-2", then every generated result will be transposed down by 2 octaves. Actually, you can change the "o"ctave dynamically, without generating a new result - when you change the "o"ctave, the change will take effect at the start of the next loop (assuming you have looping turned on).

By default, Expresso uses 3 MIDI channels for the output, starting with channel 1. You can see the "3" value next to the "#" label. If you set this to "1", then only channel 1 will be used. Likewise if you set it to "6", then channels 1 through 6 will be used. The "c" value controls the starting channel - the default is "1". If you set this to "5", and set the "#" value to "2", then the result will use two channels - 5 and 6.

By default, the results are "stepped" to sixteenth notes. You can change this by using the "More->AutoStep" menu. If you set AutoStep to "Off", the results will be quite dense, unless you set the "#" of channels to something low (like 1). If you set AutoStep to "Step some to 32nd", then the result will be 32nd notes for a measure, and unstepped for a measure, then 32nd notes again for a measure, etc.

By default, the result contains a continuous stream of notes. The "r" menu (whose default value is "All") can be used to select subsets of the notes. For example, if you set the "r" value to "1 of 3", then only 1/3 of the notes will be selected in the result. This can open up some space, and give interesting rhythmic elements.

KeyKit multitasks well, so you are encouraged to create multiple instances of the Expresso tool, and have them playing simultaneously. By default, the "starting time" is quantized to 4-beat measures, so the loops of multiple Expresso tools, playing simulatenously, will be synchronized. You can control the starting quantization with the "More->Start Quant" menu.

By default, Expresso results contain no patch change messages. If you select "More->Random Patches->On", the results will contain random patch change values on each channel. The results will of course depend on what kind of synthesizer you have.

The "v" menu lets you adjust the volume of the result. For example, if you set the "v" value to 90, then the velocity values of the results will be adjusted so that they average at least 90.

The expression transformations that Expresso uses are taken by default from the lib/default.exp file. You can look at that file to see what they are, if you're curious. If you want to use a different set of transformations, you can produce your own *.exp file and use "More->Set Transformations" to load it. Initially, though, you should use the default.

After generating a new result, if you are curious about the expression that produced the result, you can type "print Gexpr" in the console, and you will see the expression.

The value of phrase X, in the expression, is initially set to a single note. You can see this note in the phrase window just below the "Gen" button. To change this phrase, play something on your MIDI input controller, and then select "More->Load Rec (1b space)". You should see the new phrase below the "Gen" button, and from then on, the value of X in any newly-generated results will be replaced with that phrase.