/ Examples / AudioIO / Looper

This example shows how to integrate Fiddle's Looper node into your practice, recording and live-performance sessions. Looper pedals are a familiar tool to most musicians. Fiddle's looper tool is a software pedal. A single Fiddle session can have many loopers running simultaneously, each controlled by your custom mappable MIDI events.

To develop Fiddle's Looper capabilities, we needed access to a typical hands-free control rig. This was exactly the excuse we needed to develop a homemade USB-MIDI device. You can easily purchase MIDI stompboxes and control surfaces but hey, that's too easy. If you are interested in building your own, we've documented and open-sourced the dbStompbox. You can find more details on github.

Frippertronics forever!

This example requires customization according to your rigging. Right-click to copy examples to your workspace

Looper Overview

Looper nodes reside in the Graph Editor and implement live sampling functionality using ChucK's LiSa ugen. Connect an audio source to its inlet. Route the outlet to either an effects chain or directly into the AudioOut node for offline storage. In a live-performance setting, you can remap input control signals from your MIDI stompbox or control surface to modify the Looper state.

In this example we develop a looper rig for guitar jamming. Most of this discussion applies equally well to vocal or really any audio looping performance.

We'll walk through the roles of each node in this rig. Broadly speaking the top row of this graph represents a typical pedal board. The signal starts at the top left and is processed by adjacent nodes from left to right. The Guitar node is actually an AudioIn. For more details on AudioIn see this example. When the signal encounters a Looper node, here GuitarLooper, the looper-magic happens.

Nodes present in the second and third rows implement hands-free control over the session.

Looper Node

The Looper Node is the star attraction here so let's start with it.

At right you see the GuitarLooper node in an active state. In addition to the usual depiction of node inputs and outputs, we see a custom dashboard of the internal looper state. During performance, the idea is to move between looper modes. You can select a mode from the node inspector parameter, but for hands-free operation you typically trigger the mode change via control-signals.

Here is the Looper's state transition diagram:

So to get looping, first transition from Stop to Record. Next, transition to Overdub to add more to the loop. If you want to jam over the existing loop without recording, proceed to Audition. From there you can switch freely between Audition and Overdub 'til the cows come home.

On Duration

Observant readers may be asking themselves how do Record and Overdub differ?

Here's the deal: the difference between record and overdub is merely that the length of the loop is determined while recording. For a pre-determined loop length, simply provide the number of bars for your loop into the Duration field. At the point that this duration has elapsed, Looper automatically transitions from Record to Overdub. If you wish to define your loop-length during performance, manually change the mode before the static Duration elapses. This same dichotomy (static vs live) also applies to establishing the tempo as discussed below.

The loop length is the shorter of the static Duration and the time at which you manually transition from Recording to Overdubbing.

Looper Parameters

Here are the Looper Node parameters. If you opt for live-modification of these parameters, it's possible that the Node Inspector won't reflect the current state of affairs. This is where the custom node dashboard should be relied upon. Just zoom into your graph's live looper nodes before starting a session.

Duration the static loop duration expressed in TimeKeeper bars. A loop's duration can't be changed in a live session. You can, however modify the loop subset as discussed below.

Slots the number of Looper slots. Each slot is an equal-duration, but otherwise independent loop context. You can think of a slot as a recording take and switch between them live. The number of slots cannot be changed during a live session. Only a single slot, the current one, can be heard at a time. If you want to hear multiple live loopers banging their heads together, just instantiate multiple Looper nodes.

Slot controls the active slot. In multi-slot operation you can move between slots with the control signal NextSlot or NextMode (held). More discussion of control signals can be found below.

Mode controls the current operating mode. When operated manually it is on you to understand and adhere-to the state-transition diagram above. In hand-free mode, the NextMode control signal manages the state transitions with a single click.

Sync controls the all-important timing of the transition from Stopped to Record. Selected between Bar, Beat or None to ensure that activity lines up in time the way you like.

Feedback controls the overdub signal loss between loops. At 1 the signal stays around forever and can easily produce a muddy result. At 0, the effect of the looper is entirely removed, only the live signal appears on the output. In this example, we've connected an expression pedal to the Feedback value via dbStompbox and CCRelayer.

Subset controls the active loop subset. Choose between Full, Half and Double.

Gain a multiplier for the output signal.

TimeKeeping

Successful looping often requires that you be keenly aware and in control of time. The TimeKeeper node supports these features to help with looping:

Tap Tempo is a control signal that can be delivered by a control surface. In this example we've wired a footswitch to deliver a Tap message. Typically you nominate a tempo prior to entering Record. The above discussion of Duration applies relative to the TimeKeeper tempo at the moment of recording.

Metronome enables an audible sound on beats and bars according to the current Metronome Style. The sound is routed directly to ChucK's global DAC. In this example we route the output of Channel directly to the AudioFileOut node. When active (as controlled by a Record button in dbStompbox), the Metronome sound won't be present in the recording. If you prefer visual feedback, disable the Metronome and zoom in to the TimeKeeper node during performance and see the measures and beats update live. At right, notice that the Timekeeper shows the signature, BPM and current time in its custom node-dashboard area. Further notice that the TimeKeeper time is also present in the Looper's dashboard and that its loop time is two measures behind the global time.

Metronome Style chooses the metronome style and is only relevant when Metronome is enabled. Options are: Bars+Beats, Bars, Beats.

Metronome Gain controls the loudness of the Metronome signal.

Managing Controls

At the heart of performance looping is the requirement to modify the session state fluidly. Whether your "axe" is your voice, a guitar, keyboards or a saxaphone, it's often the case that a computer keyboard or mouse isn't the right tool. This problem is usually solved with a MIDI or USB control surface. The idea is to assign important events to keys, foot pedals, dials or sliders that are adjacent to your instruments.

In this example we employ dbStompbox which is just a homebrew MIDI controller with 6 momentary foot switches and 2 expression pedals. A simple Amazon search reveals a number of similar options ranging in price from US$49 to US$350.

Because selecting a control surface is a personal choice, it's inevitable that this example will require modification to attain a glorious result. So our goal here is to teach fishing, rather than to deliver fish.

CCRelayer Node

The CCRelayer's job is to remap/rename incoming CCs and route them to specific targets. Following the documentation for your control surface, the first step is to decide which buttons (knobs, etc) to assign to which actions. In the case of dbStompbox we have:

Description	CC Name	Action
Pedal 1	CC8	Wah Wah Pedal
Pedal 2	CC9	Looper Feedback
Footswitch 1 (left)	CC64	(available)
Footswitch 2	CC65	(available)
Footswitch 3	CC66	Enable Record
Footswitch 4	CC67	Stop Looper
Footswitch 5	CC68	Tap Tempo
Footswitch 6 (right)	CC69	Looper Mode

Here's our example graph reorganized to highlight the role of CCRelayer in the remaining discussion. The important consideration is that we'd like our single control surface to deliver different signals to different nodes. For example we want pedal 1, CC8 to route to LkCryBaby2/Wah (on Ctrl0).

Controller is the input CC source (eg MIDI device) whose signal we wish to remap and relay. In this example we connect dbStompbox which is just an instance of the CCMidiDevice node with its correct MIDI identifier.

RelayTarget parameter selects the downstream target(s). When relaying an event to a particular output, all nodes downstream from that port receive it (broadcast). The RelayTarget parameter can be automated. Special values include None: -2, All: -1. In this example we select All because most of the work is done by the optional Routing table.

Routing is a table that expresses how an input parameter is routed to an output port. Here we have six routing rules. These rules are evaluated for each input signal. Any rules that match produce a result. This means you can have one input signal remapped to N different output ports, each with a different name. Referring to the graph image above you can infer that Footswitch 5 controls the Tap parameter and is targeting the TimeKeeper connected on output port 3. Also, in this example we opted to overload the NextMode control signal to also trigger the NextSlot behavior. This is accomplished thanks to special support built into the Looper node. If you hold the NextMode button down for greater than 1.5 seconds, a NextSlot request is inferred. The advantages of this approach includes improved useability and footswitch conservation.

Remap allows you to connect any number of Remapper nodes whose purpose is to modify the values of matching control signals. In this example, the Remapper node resolves two issues:

1. The home-rolled expression pedal only delivered values between 0 and .91. A range of 0 to 1.0 is preferred.
2. The Looper's Feedback parameter gives a more natural/controllable result when the parameter values range over .3 to 1. Specifically the zone below .3 deadens the signal too quickly. The remapper prevents this.

Remapper Node

The Remapper Node is used by CCRelayer to modify the values of incoming control signals. You can instantiate and connect multiple Remapper nodes but shouldn't connect more than one per unique signal name.

Match is the name of the input signal to match.

InputMin the value to consider as the minimum input value. If the incoming value is below this number it will be clamped.

InputMax the value to consider as the maximum input value. If the incoming value is above this number it will be clamped.

OutputMin the value to produce when the input is at its minimum.

OutputMax the value to produce when the input is at its maximum.

Style the style of the "connection" between OutputMin and OutputMax. Common choices include Linear and Exponential.