Sunday, 1 July 2018

An 'Extreme' Multiplying LFO for MaxforLive


LFOLFO is an experimental 'Multiplying' LFO. It is based on the idea that being able to switch the range of an LFO can be used to generate a number of interesting audio effects, and so the design is optimised to enable easy control of the Rate and Multiply controls. The prototype was produced as a response to a question posed by Russell Alderton on the 'Max For Live Users' Group on Facebook, and it has undergone extensive development since then.

The Rate (Frequency) of the LFO can be modulated via two controls: Rate and Multiply. The Rate control is a conventional frequency control, whilst the Multiply control has four modes that provide several ways to affect the frequency. A multiply value of 'x 1.' produces an output frequency as shown on the Rate control, whilst a multiply value of 'x 0.5' produces an output frequency of half the value shown on the Rate control, and a multiply value of 'x 2.' produces an output frequency of twice the value shown on the Rate control.

The Rate and Multiply controls both have their own dedicated Sub LFOs, which can be used to modulate them, and this is shown graphically in a display underneath the controls. The LFO output waveform is shown as a backdrop to the whole MaxForLive device, thus providing a 'history' of recent changes to the waveform.

Each Sub LFO has multiple output waveforms, and the waveform selection of Sub2 can be controlled by Sub1. The output waveform of the LFO itself can be selected using a vertical selector, or via two modulation modes: one that counts the number of cycles that have been output, and a second mode that uses a third Sub LFO (Sub3). Both modulation modes use a probability grid that can provide sophisticated control over the sequencing of output waveforms.

The output waveform can be further processed by three controls: Smooth, S&H and Decimate (which do what their titles suggest). Finally, Offset and Depth controls. plus an Invert button allow fine tuning of the range of effect on the controlled parameter - which is selected using the 'Map' button.

Sync

Conventional Digital Audio Workstation (DAW) LFOs are either free-running, or synched to the DAW transport. LFOLFO provides a different type of sync that is intended to explore an alternative approach. A selection from a number of timing sources can be used to reset the LFO waveform, and this provides an 'Event Sync' that gives a number of interesting ways working with musical events instead of being rigidly locked to a timebase.

The UI from left to right

LFOLFO has a lot of controls that it uses to provide a wide range of advanced functionality. The settings above are a good starting point for learning - they are a kind of 'Neutral' setting. From left to right, the controls are:

Storage

LFOLFO provides 9 'memories' that can be used to store and recall the state of all the controls. To store a setting, hold down the SHIFT key and click on one of the 9 boxes. Grey boxes are empty. Purple boxes contain a saved setting. The white box is the currently selected setting. If you over-write a box then the previous contents cannot be recovered - this is colloquially known as a 'face-palm' error.

Event Sync

The large selection box enables the selection of 'events' that can be used to reset the LFO output phase. The reset phase is set using the 'Phase' retry control that is underneath the selection box. The top selection is '=Not-Synched=' and this is the Free-Running mode. The next selection options are for MIDI Notes in the track clip:

- AnyNote resets the phase for any MIDI Note.
- AnyChange resets the phase for any new MIDI Note. Any repeated notes are ignored.
- Note0 only resets the phase for Note 0, the lowest MIDI Note. This note is not used very often...
- Note0Velo1 only resets the phase for a Note 0 MIDI Note with a Velocity of 1. A velocity value of 1 is very quiet.

The next selection options use the Sub LFOs. Sub1, Sub2 or Sub3 can be used to reset the phase of the LFO, as well as a special reset that uses Sub3 and the waveform cycle Count (shown on the far right hand side).

The reset happens as soon as the event is processed by the device, and the value can be set using he 'Phase' control. If the event frequency is less than the 'Rate' then one or more cycles of the output waveform will be output. If the event frequency is higher than the 'Rate' then cycles will not be completed because the reset will happen before the cycle can complete.

Sub1

The first sub LFO can be used to modulate the 'Rate' control. The 'Sub1' rotary control affects the rate of the Sub LFO, whilst the 'Depth' rotary control affects the amount of modulation. The selector box sets the output waveform. When Sub1 is used to modulate the 'Rate' control then a graphical display behind the rotary control will show the modulation.

The Sub1 LFO can also be used to control the output waveform of the Sub2 LFO. If the frequency of Sub1 is greater than Sub2, then Sub2 will output incomplete cycles of its waveform. The selection of the output waveform is in sequence, from top to bottom, and then repeats. No other waveform sequences are available in this version... The button has two settings: 'Off' has no effect on the Sub2 output waveform, whereas 'Mod' will repeatedly sequence through the four waveforms.

Sub1's modulation of the 'Rate' control can be used for a number of effects. Using a Sine waveform produces traditional smooth 'up and down' variation in the frequency of the LFO. The triangle waveform gives a more abrupt change of direction and gives a more synthetic effect. The two sawtooth waveforms are particularly good when Event Sync is used, because they can produce a number of 'rise' or 'drop' effects, where the frequency of the LFO rises or falls linearly. Note that one of the advantages of using Event Sync is that when the frequency of the events is less than the LFO 'Rate', then several cycles of the output waveform will be produced, whereas if the event frequency is greater than the 'Rate', then less than cycle of the waveform will be produced. So by adding MIDI Note events into the track clip, very precise control of the LFO output can be obtained. 

Sub2

The second sub LFO can be used to modulate the 'Multiply' control. The 'Sub2' rotary control affects the rate of the Sub LFO, whilst the 'Depth' rotary control affects the amount of modulation. The selector box sets the output waveform. When Sub2 is used to modulate the 'Multiply' control then a graphical display behind the rotary control will show the modulation.

There are four modulation modes for the Multiply rotary control, selected using the horizontal selector box on the lower edge of the device:

- Linear is a conventional modulation where the modulation increases linearly.
- Power increases the modulation in powers of 2.
- PowerHalf increases the modulation in quantised half powers of 2.
- PowerQnt increases the modulation in quantised powers of 2 (0.25, 0.5, 1, 2, 4 8, 16...)

Rate

The Rate road control is the main control of the frequency of the LFO. The output frequency is shown in Hertz. The modulation is shown graphically underneath the control.

Multiply

The Multiply control is a secondary control for the frequency of the LFO. It is rather like a 'range' control, but it can be modulated, and the rate and character of the jumps in LFO frequency can be controlled via the waveforms and the Sub1-Sub2 modulation button. Careful use of the Multiply control is the key to making the most of the functionality provided by a Multiplying LFO. Yes, you can use LFOLFO to vary a parameter with slow, smooth up and down changes, but this does not exploit the device to its full potential.

Try increasing the Multiply rotary control in each of these modes to see the effect on the 'Multiply' value. The 'PowerQnt' mode is specifically designed to change the rate in powers of 2: x .125, x .25, x .5, x 1, x 2, x 4, x 8, x16...

Vertical bar

The vertical bar shows the LFO output at the current time, and is not a control.

Waveform

The large selector box in the centre of the device serves two purposes, dependent on the mode set by the 'Waveform Mode' selector on the right - which has three modes: Select, which allows direct control of the LFO's output waveform via the selector box; plus Count and Mod3, which both use the grid in the middle of the device to choose waveforms, and the selector box then becomes an indication of which waveform is currently being output. In the Select mode, the grid, plus the Columns, Sub3 and Count rotary controls all do nothing. In the Count mode, the Columns and Count controls set the number of columns in the grid, and the number of cycles of waveform output that need to happen before the waveform changes (controlled by the cursor moving across the grid). In the Mod3 mode, then the Columns and Mod3 rotary controls are active, setting the number of columns and the rate at which the cursor moves across the grid.

The Grid

The grid is only active in Count and Mod3 modes, and allows the sequencing of waveforms to be specified. White squares indicate which waveform will be output when the cursor is in each column, an the vertical Waveform selector box shows which waveform is currently being output. If more than one square in a vertical column in the grid is white, then the output is randomly chosen from the white squares. So if there are two white squares in a vertical column, then the corresponding waveform will be chosen 50% of the time, on average. If there are three white squares, then each waveform will be output 33% of the time, on average. In the example shown above, there is just one white square in each of the two active columns, and so the corresponding waveform is chosen 100% of the time. This means that in Count or Mod3 modes, the first waveform to be output will be the Saw Down, followed by the Saw Up.

If you draw a line of white squares from the top left hand corner of the grid to the lower right hand corner, then each waveform will be played in sequence, just as in version 04. If you draw the opposite line, then the sequence will be reversed. The grid allows you to specify any sequence of waveforms, plus it allows probabilistic control over waveforms, which allows long complex waveform outputs. In summary, LFOLFO provides humungous power for creating output waveforms!

Once the waveform has been controlled using one of the three modes, then further processing can be carried out on it. This happens in the darker vertical box containing the 'Smooth', 'S&H' and 'Decimate' rotary controls. 

Smooth

The Smooth rotary control is a low pass filter that removes the sharp edges in the output waveform, but it also reduces the amplitude - so you may need to use the 'Depth' control to increase the size of the LFO output waveform. Remember that the 'Depth' control affects the output amplitude of the LFO waveform before the Smooth control.

S&H

The S&H rotary control adjusts the rate at which the LFO outputs its waveform. This has the interesting side effect of slowing down the scrolling speed of the background waveform display - but it does not change the rate or frequency of the LFO!

Decimate

The Decimate rotary control adjusts the resolution of the LFO output waveform. In the '0' position, then the LFO waveform is smooth, whilst increasing decimation values makes the output increasingly jagged until at '2.0' then there are only two values (maximum and minimum). You can still use the Smooth and S&H controls on a decimated waveform, so these three controls should be seen as a flexible way of adjusting the output waveform to your specific requirements.

Once the final waveform has been set, then the final section (on the right) does the mapping of the LFO waveform to the parameter that is going to be controlled by the LFO.

'Normal' or 'Invert' button

This button controls how the parameter is controlled by the LFO output. 'Normal' is the same as the vertical bar, whilst 'Invert' is turned upside down, so that high values of the vertical bar give low parameter values.

Offset

The Offset rotary control adjusts the output of the LFO. Normally this will be left in the default '0' position, but some parameters and other settings may require it to be changed. The output waveform display that forms the background to the device is the key to using the Offset control - you should adjust the offset so that the waveform is not clipped at the top of the bottom. (although you can use this as a deliberate effect if you wish)

Depth

The Depth rotary control adjusts the size of the LFO output (which is why it is the right-most control!), and 100% is at the middle position, so you can deliberately output larger values that will be clipped. The Depth and Offset controls will often be used together to get the exact parameter changes that are required. 

Unmap and Map

The Unmap button is only available when a parameter has been mapped using the Map control. The Map button is easy to use - just click on it and then select the parameter that you want the LFO to control. A good starting point is filter cut-off frequency in the 'Auto Filter' device. When you have correctly mapped a parameter then the name of the parameter will replace the 'Map' text in the button, and the 'Unmap' button will become available. If you click on the 'Unmap' button then the mapping to that parameter will be lost - and the only way to remap it is to carry out the mapping process again.

Getting LFOLFO

You can download LFOLFO 0v06 for free from MaxForLive.com.

Here are the instructions for what to do with the .amxd file that you download from MaxforLive.com:

https://synthesizerwriter.blogspot.co.uk/2017/12/where-do-i-put-downloaded-amxd.html

Modular Equivalents

In terms of modular equivalents, then reproducing this functionality in my modulars took anything from 10 to 14 separate 'basic' modules, with lots of patch chords (and some limitations and compromises), so I would rate this version as being about 12 ME.


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