LOGIC NOTES

Monitor with Effects While Recording

Published in SOS March 2002
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Technique : Logic Notes

A power-user trick for configuring the Environment so that you can monitor with effects while recording, as well as some guidance on incorporating external effects hardware into your Logic system. Plus a selection of tasty tips, including a way to get better hi-hat parts using a drum controller.

You can configure any Audio object as an input object by selecting one of your audio inputs in the Cha field of the object's Parameters box.

Aside from the inevitability of at least some degree of through-signal latency, Logic users who are trying to run completely self-contained systems — ie. using no external hardware other than an audio interface/soundcard — come up against one particularly frustrating limitation when overdubbing and doing drop-ins on audio parts. If you are trying to replicate the traditional mixer/tape-recorder scenario for overdubbing, where you monitor via the recorder's own input/off-tape switching, your Logic system will be set up with Software Monitoring switched on and Auto Input mode selected. This allows the targeted track to playback until you drop in, whereupon the monitoring will automatically switch over to the live input signal. The difficulty lies in the fact that, whilst you can apply effects to the track playback to assist in creating a comfortable monitor mix, those effects will disappear the moment you drop in, as the Audio objects used for recording do not support real-time effects on live audio input. However, there is at least one way to work around this...

Any Audio object which has been designated as an input will support real-time effects on input signals, but input objects, of course, can't be recorded. The obvious answer would seem to be to share the input between the track Audio object and the input Audio object, recording via the former and applying effects via the latter. But when a common input assignment is shared by both a track object and an input object, the track object takes priority as soon as it enters Record, thus 'stealing' the input signal and killing the effects in the monitoring.

The pragmatic solution therefore lies in feeding your signal into two physical inputs simultaneously (ie. arrange a split feed into two line inputs of your interface if you are using an external mic amp or mixer, or just use a passive XLR 'Y' splitter into two mic inputs on your interface if you are using a totally self-contained setup). You can then configure an input object that is fed from one input, and a track object which has the other input as its source.

Now set up pre-fader buss sends to the desired effects on the input object and drop its fader all the way down. This gives you an effect-only feed from the input signal which will not be muted by the track object going into Record (as the track object is now fed from a different input). The point of configuring the input object's buss sends pre-fade with the fader down is to avoid double monitoring of the dry signal when you drop-in. The only side-effect is that the effects send from the input object will remain live even during playback.

If you prefer to work with live monitoring at the same time as off-track monitoring when overdubbing, you can leave the input object's fader up (and leave the sends as post-fade). The Auto Input mode will ensure that the recorded track is killed in the monitoring while recording, and the mic will remain live the whole time. The only side-effect here is that the signals from the input and track objects will combine during the drop-in, increasing the level of dry signal.

In this configuration you will have effects available to the track signal, via the track Audio object, with precisely the same effects able to be achieved on the input object's through-monitoring signal by matching the buss send value (obviously, you have to be sending to the same effects buss!). If the fader of the track object is at unity gain, matching the buss send numeric value between the input object and the track object will result in precisely the same subjective effect level (a pre-fade send is equivalent to a post-fade send with the fader at unity).

It's not elegant, but it does work! If you can live with the latency — which with the current generation of computers is certainly getting well into to the sub-10mS area that many performers can tolerate — then a self-contained Logic system really can offer you the familiar comfort zone of overdubbing and dropping-in with your signal placed fully in context by monitoring effects.

Despite the proliferation of excellent plug-in effects available to Logic, decent hardware reverbs tend to outperform their software counterparts, simply because native plug-ins need to conserve CPU power. However, providing you have an audio interface with at least one spare output, it's easy to hook in an external mono-in/stereo-out hardware reverb.

Exactly how you set up your system depends on your audio interface, which needs to be two-in, four-out at the very least. With a two-input card, you'll need to repatch after recording so that you can use the two inputs as effects returns while mixing, but if you have an interface with four or more inputs, you may be able to leave two configured as recording inputs and two as effects returns.

The secret to making all this work is how you set up the Audio objects in the Logic Environment. If you have an effects box with a physical input gain control, then you can simply connect it to one of the physical outputs of the audio interface and then set post-fade sends to feed that output. You can check whether this is working or not by looking at the input meter on your effects box. If you get a level with the send turned up and audio playing, then you've got it right.

In the event that your effects box has no input gain control, you'll need to create a master send fader, which is achieved by creating a buss Audio object and then directing all the channel sends to that buss. To route the buss signal to the single output, you'll need to route the buss object to the correct output pair and pan it hard to one side. Now the buss object's fader can be used as the master send control. The last job is to set up a stereo reverb return, which is simply achieved by creating a new stereo Audio object and setting it up as an input object routed to your main outputs.

One thing you must remember is to set the wet/dry mix on the effects unit to 100 percent wet, otherwise the dry component of the signal will phase with the source sound because of the computer's latency delay — this is the usual practice for adding reverb or delay via send/return loop. However, in the event that you wish to use an effect that requires a dry component, such as chorus or flanging, set the channel send to pre-fade and then pull the channel fader down to zero. This will kill all direct sound, but still feed the channel signal to the effects unit, where the wet/dry balance can be managed independently. On systems with audible latency, you may need to advance the audio tracks being processed by the equivalent number of milliseconds (just add negative delay in the Arrange window) to achieve accurate timing — Logic's plug-in delay compensation can't help you when you're using live inputs.

More Realistic Hi-hat Control     One of the limitations of drum controller pads such as the Roland Octapad units is that you can only use a footswitch for a hi-hat pedal. As any drummer will tell you, the hi-hat has multiple levels of 'open-ness', and a simple on/off switch simply doesn't do the sound justice. Fortunately, Logic user Dr Paul Langtry has found a way to configure the Environment to get around this, allowing you to use MIDI Continuous Controller data from a MIDI expression pedal to switch naturally between six different hi-hat samples ranging between closed and open. What you need to do is combine the controller data with the note data (the Octapad has a volume pedal input which is converted to MIDI and mixed with the notes automatically), and then to send it to a new Transformer object which rescales the pedal's controller values from the normal 0-127 range to 0-5 — this requires you to divide the second data byte by 24. This Transformer object should then be cabled to a Cable Switcher object (this is a type of Fader object which can be created from the Special submenu in the New menu's Fader submenu) set up such that it responds to the MIDI controller value your expression pedal is generating. Finally, cable the outputs of the Cable Switcher to five Transformer objects, which transpose the hi-hat MIDI note (as generated by the drum controller's hi-hat pad) as appropriate to trigger the progressively more 'open' samples. The outputs from these, and direct from the switcher, can then be routed to a Sequencer Input object for recording. You can see the complete setup in the screen below. Mike Senior

Avoid Eyestrain — Use Giant Transport Window Read-outs!     There are times when you need to be able to read the Transport window's timecode or bars/beats display from a distance — for example, when sorting out synchronisation with other pieces of equipment at the other end of your control room. In such cases, it can make life easier if you open up a second instance of the Transport window, selecting the appropriate Giant Display option from its drop-down menu. This will fill the entire Transport window with a large read-out. If this still isn't large enough for you, then you can always increase its size by going back to the window's pull-down menu and selecting a higher number from the Size submenu. Mike Senior

Logic Tips     If you have edited Arrange-window regions from within the Sample Edit window, you'll probably have noticed that moving the Anchor point causes the audio to move in relation to the Arrange window's time position bar. If you don't want this to happen, select Update Arrange Position from the Sample Edit window's Edit menu. Mike Senior If you find yourself cabling between Environment Layers, it's easy to forget which other object and layer you're connecting to. In such cases the Select Cable Destination entry in the Environment window's Edit menu can save time searching through your environment and scratching your head. Sam Inglis Though many people like to work with note durations in the Event List, I usually prefer to see exactly where the MIDI Note Off message occurs — this makes it easier to see how far notes overlap. To switch to this mode, select Length As Absolute Position from the Event List's view menu. Mike Senior If you're wanting to use old tape or vinyl recordings in your Logic Song, you'll be interested to know that the Sample Edit window has a Silencer function in its Factory menu which reduces the levels of tape hiss and vinyl noise. The quality isn't world-beating, but you can still do a useful amount of cleaning up before your audio begins to suffer too much. Mike Senior

Current Versions     • PC: Logic Audio Platinum v4.8.1 • Mac: Logic Audio Platinum v4.8.1