Cumulus is a granular sampler which radically transforms sample content by breaking it into tiny slithers of audio called grains and reorganizing them to form new sounds. Cumulus is capable of a wide ranges of timbres: from evolving atmospheric soundscapes; to organic physical textures.
Up to eight Scenes can be created; a Scene corresponding to a particular sample position and set of synthesis parameters. Scenes can be played in realtime via MIDI, or arranged internally using the built-in sequencer.
Cumulus is available free on the cover-mounted DVD of Computer Music magazine from issue 170 and onwards. Cumulus is supported on Mac OS X (VST, AU, RTAS, and Standalone), Windows (VST, RTAS, and Standalone), and Linux (VST, Standalone), and natively supports 64-bit for VST, Audio Unit, and Linux Standalone formats.
I've spent a little time improving the Pure Data MIDI Step Sequencer patch that was originally posted here. This new version adds selectable step divisions, and a fairly decent swing algorithm. The code has been tidied up somewhat too; in many places, lists provide a much more cohesive data structure than the separate pitch and velocity streams that the first version used.
Presented here is a very basic MIDI Step Sequencer for Pure Data. It's locked to playing 16th notes, but the tempo and number of steps can be changed. The pattern can also be transposed. Finally, it comes with a decent random pattern creation system, ideal for that 'dead batteries in a 303' style sequence.
The top right window displays the pitches for the steps, selectable between -12 and +12 semitones. The center right window the velocity (where 0 means no note is played). The bottom window shows the currently playing step. Obviously, as a MIDI Sequencer, it doesn't actually produce audio on it's own: you'll need to route the MIDI to the instrument of your choice.
The patch itself is fairly simple; there's nothing in there a novice Pure Data-er familiar with basic messaging and lists couldn't grasp. Adding multiple pattern support would be a simple, yet interesting addition for the eager coder.
Here's a short audio demo of it at work: here, MIDI is output from Pure Data using the Mac IAC MIDI Driver (use MIDI Yoke on Windows) into Aspect, which is playing a nice analogue mono synth bass sound.
Start with a blank program configuration by clicking File / New Program.
A sequencer connected to a synth will trigger a succession of notes, where the volume contour of each note is controlled by the synth's amplifier envelope. This triggered envelope can be emulated by instead using a repeating modulation source to shape the note volume. We'll use a percussive volume contour: a quick attack, and slow decay. A Sawtooth LFO (Low Frequency Oscillator, in this case LFO1) will provide the shape we need, but from the following display we can see a problem: Aspect's Sawtooth LFOs ramp upwards, which is equivalent to a slow attack, and instant decay.
This is easily corrected by linking the LFO's output into an Inverter component (we'll use Inverter1 in this example). As you'd expected, this generates the shape we need (see diagram below.)
Which, when connected to the Output Amp Modulation and Synced to a rate of 1/16, produces the following 16th note pattern:
The remaining 2 LFO components will be used to make the notes within our sequence play at different pitches. Both LFO2 and LFO3 are set to Synced Square waves. LFO2 is set to a rate of 1/8, and LFO3 to a rate of 1/4. when we align all three LFO signals we can clearly see a short sequence that repeats every four 16th notes:
The LFOs now need to be connected up as modulation sources to their required destinations. LFO2 should go to Oscillator1's second Pitch Modulation slot, with a depth of 2.00 semitones. (Remember that holding down the Shift key whilst dragging a rotary control will allow for more precise changes. This is useful when exact modulation depths are required.) LFO3 should be connected to Oscillator1's third Pitch Modulation slot, this time with a depth of 7.00 semitones.
With LFO2's Square modulation output causing Oscillator1's Pitch to move between 2 semitones up and 2 semitones down every 16th note, and LFO3 causing a modulation of 7 semitones, up and down, each 8th note, we get the following jaunty pattern repeated every four 16th notes:
Due to Aspect's flexible semi-modular architecture, even without a dedicated sequencer interesting melodic patterns can be created. We've explored the simplest example - using LFOs to control a note's pitch - but for the more dedicated sound designer, Aspect's audio rate modulation sources and Patch section components provide the building blocks for a wealth of complex sequencer-style patterns.
Aleatoricism is defined as "art created by exploiting randomness". From Pierre Boulez's experimentation with controlled chance to Brian Eno's use of Koan to produce Generative Music 1, it's a well explored area of music composition. Even Roland's TB-303 offered prospects for the aleatoric explorer: leaving the battery removed for a short time corrupted the sequencer memory, generating 64 tracks of random acid.
Elysium is a probabilistic sequencer, developed by LucidMac Software and available (for free) on Mac OS X. It's a pure sequencer, not a synthesizer or a host. It doesn't produce any sound itself, but generates a MIDI stream that can be used to drive any MIDI consuming application or hardware. Despite this, syncing with a DAW such as Logic or Live running on the same machine as Elysium is completely pain-free; no additional configuration was required to get it working.
The Elysium interface is made up of a grid of hex cells, each representing a note of a certain pitch. Playheads move across the grid in sync with the tempo. By placing tokens on cells, the playheads (which are spewed out at specified tempo from a Generate token) can be made to perform an action: a Note token causes the note on the underlying grid to be played; a Split token divides a single playhead into several, each launching out at different trajectories; a Rebound token bounces the playhead back in the opposite direction.
Tokens can also be assigned probabilities, only performing their functions on a roll of the virtual dice: 50% of the time, this playhead will rebound; 25% of the time, this note will play. Using this system, constantly varying pieces of music that would be tricky to compose using traditional sequencers can easily be easily generated.
Watching playheads creep across a grid is somewhat reminiscent of John Conway's cellular automaton Life simulation. The interface is simple to use, but not necessarily intuitive at first glance. Reading the introductory documentation, which is scant but does well in explaining the basics, is advised.
Elysium is currently only available for Mac OS X. It was recently released as open-source under the MIT license, so there is a chance of seeing a port to other operating systems. More information about Elysium can be found at http://lucidmac.com/products/elysium
