Input monitoring using Audio Unit (but no on main input)

So far I had some great fun with GTL on my iPhone 5S. Thanks, guys! :-)

I noticed though that when I set an FX to a loop (like a Tonebridge effect for my guitar), it will be only applied when the loop is played back, not when recording it. This is a pity.

I know that I can set an FX to the main input, but then it will be applied to each and every input, which is not useful. For example, when having a Tonebridge effect applied, I don't want to apply it when recording a vocal, so I will have to remove it manually, and re-add it later.

Is there a way to achieve what I want?

Thank you.


  • Hi Josh,

    The only way to do this is to use AUM or Audiobus to as an input mixer for your instruments. You will be able to add different effects to each input/instrument when recording them into GTL. Let me know how you get on.
  • Hey Jack

    I know that I can use Audiobus to add effects and send the mix to GTL. But I need to switch quickly between different effects on the SAME instrument (input) when recording different loops.

    For example, I want do the following when doing a cover of "Wish you were here" (Pink Floyd, compare to for the original recording, and to for the song parts):

    1) Acoustic Guitar Intro: Record loop 1 in group 1 (from approx. 0:00'' to 0:42'')
    - For this, I want to use effect A from Tonebridge on input 1 (my acoustic guitar)
    2) Immediately record loop 2 in group 1 with the lead guitar (from 0:43'' to 1:17'')
    - For this, I want to use effect B from Tonebridge, still on input 1
    3) Verse 1: Immediately record loop 1 in group 2 with the guitar strumming (from 1:18'' to 1:51'') while singing ("So... so you think you can tell...")
    - For this, I want to use effect C from Tonebridge still on input 1
    - And I want to use my microphone on input 2 (preferably with some reverb from an AU)

    From now on, I'm set up with everything I need:

    4) Verse 2: I keep on playing group 2 (from 1:52'' to 2:21'') while singing ("Did they get you to trade...") into input 2
    - Optional: I could even record some percussion using my cajon on input 3
    5) Interlude: I let group 1 play (from 2:22'' to 2:58'') and can sing (input 2) and/or play my guitar (input 1) to add some of the "doo-diddle-doo" vocals/sounds
    6) Chorus: I let group 2 play (from 2:59'' to 3:29'') while singing ("How I wish...") into input 2
    7) Fadeout: I let group 1 play (from 3:30'' to end) while doing some more improvisation with singing ("doo-doo") and maybe even adding some synthesiser chords using an external keyboard on input 4

    I hope you can see how critical it is for me to be able to switch effects quickly in between recording loops, and that the effects are applied directly while recording.

    I haven't experimented much with Audiobus yet, maybe I can solve those problems there? Maybe it is possible to create virtual inputs with predefined AU effects on each one of them, and in GTL I can simply connect to those? For example:

    • Virtual input 1: Input from physical input 1 (guitar) with Tonebridge effect A applied
    • Virtual input 2: Input from physical input 1 (guitar) with Tonebridge effect B applied
    • Virtual input 3: Input from physical input 1 (guitar) with Tonebridge effect C applied
    • Virtual input 4: Input from physical input 2 (microphone) with reverb applied
    • Virtual input 5: Input from physical input 3 (cajon)

    Can something like the be achieved using Audiobus? Or with any other app?

    By the way, I have a Zoom U-44 ( with the EXH-6 capsule (, offering me 4 inputs.

    Thanks a lot for help and inspiration. :-)

  • edited November 2019

    Morning @josh,

    Nice to see you back :) It's a tricky one.

    If I understand correctly:
    1. You need to sub mix your multiple instruments into GTL.
    2. You need to select and input effect patch on Tonebridge.

    As for sub mixing, yes you will need Audiobus or AUM. Personally I use AUM and just leave all my instruments turned up. Then I use a switchable mic to turn on the mic when necessary and turn down the instrument volume when not using it.

    As for selecting the input effect, the best way would be to control Tonebridge via MIDI and switch the effect preset that way. Tonebridge could be added to each guitar channel in AUM. Either that or you set up duplicate guitar channels in AUM with different effects and mute the ones you are not using.

  • You can set fx (includding AUv3 fx right @Jack?) inside every clip so you can record into them “clean” but they will replay themselves “effected” the very moment they start...
    Not the perfect solution but useful for sure!
  • @dubbylabby said:
    You can set fx (includding AUv3 fx right @Jack?) inside every clip so you can record into them “clean” but they will replay themselves “effected” the very moment they start...
    Not the perfect solution but useful for sure!

    Hi @dubbylabby,

    Yep that is correct.

  • edited November 2019

    Thanks, guys. The really tricky thing is the necessity of switching between guitar effects on the fly, but exactly between then ending of recording one loop and starting the recording of another loop.

    Using MIDI for this feels quirky, as it's still a very manual task (unwanted artefacts could occur, e.g. when switching the effect a bit too early or too late).

    I think a first useful step into making switching easy and fast would be the possibility to apply any FX already when recording a loop (instead of applying it when repeating them). A simple switch in the settings could do the trick. This way I could prepare my effects and stuff in advance and would only need to switch between loops. Is there any technical limitation which prohibits this?

  • edited November 2019

    I played around even more, hoping to find a way to switch between different "instruments" (inputs plus effects) that could work for me (which means: as quickly and precisely as possible while recording loops).


    When I use Input 1 (guitar) and add a Tonebridge effect, then send the output to GTL, I notice that in GTL, the input options change from my system audio to the following options:

    • Audiobus 1+2
    • Audiobus 1
    • Audiobus 2

    This looks promising at first sight. I try to add many more slots in Audiobus (all sending output to GTL), hoping that additional "Audiobus 2, 3, 4..." options would appear. But sadly no, they don't.

    Am I restricted to only two channels here? And what's the exact source of channel 1, and of channel 2, respectively, originating from Audiobus? In Audiobus itself, I don't see any hint.

    Furthermore, I notice that I can't add any MIDI events for switching input to those channels. So even if I could make use of different Audiobus channels, this wouldn't work for me anyway, as I can't switch quickly between them.


    I went and bought AUM at the app store, hoping to find new solutions there. And hey, it looked very promising at first sight!

    I found that I could send the output from AUM to 8 different "IAA / AB output" channels, which then can be used as input source directly in GTL! Nice, so I could define 8 different "instruments" within AUM, then load them in GTL.

    But again: I can't bind them to MIDI events. Bummer. :-(

    Also, when switching between those channels manually, there seems to be quite a delay (around 1sec) until the selected channel kicks in. Not ideal for a live performance.


    Digging around a bit deeper, I guess I have finally understood the concept of MIDI from within Audiobus (and AUM): using an external MIDI controller, I guess I could switch between inputs and FX within Audiobus (or AUM), so I wouldn't need to change anything in GTL itself.

    Could be a solution, but I would need to get a MIDI controller for this (so far I'm only using my standard Apple Magic Keyboard, and I LOVE the keyboard bindings in GTL).

    Final verdict:

    I still feel something is much too complicated here. GTL seems to have all the functionality already built into its core for targeting different inputs and AU FX, it's just lacking an easy way of:

    • pre-configuring them per track

      • although it already allows to configure FX per tracks (it simply doesn't apply them while recording)
      • and the possibility to choose the input per track would be a nice addition, too
    • or switching them quickly and easily on the fly

      • while it allows switching system inputs per MIDI, it does not for Audiobus and IAA inputs

    Maybe I'm an "exotic" user of GTL, but to me, all the Audiobus and AUM compatibilities seem nice and advanced, but they don't solve my most important use case so far (which I feel would be solved much more easily in GTL itself).

  • This is related to multiple outputs and audio stages. ATM GTL doesn't supports multiple inputs/outputs so inputs are funnelled using AB3/AUM being these some kind of virtual pedalboard. The main issue will be audio recorded into clips is already effected on its source versus the fx per clip approach of GTL which keeps the audio clips clean files and AUv3 (fx) are applied over that RAW file.

    I understand your demand/approach but multiple inputs/outputs aren't trivial coding additions. If you need more flexibility meanwhile GTL gets those features (these are related to the future editor if you ask me) I will suggest three options.

    If you top priority is keep the song structure approach that GTL has... go Ableton Live. It has all you need being more or less the fusion of GTL/AUM/AB3 and full plugin support at any audio stage. You can build fx racks and submixes like AUM/AB3 all fully midi/key mappable. It has clip launch and record and even a dedicated looper plugin.

    It has also some drawbacks if you ask me (again) starting to need a full computer to use it and ending by lots of unnecessary features for most loop-artist needs. In fact GTL lacks in the same problem since the majority of loop-artist can't see the need of song structure.

    Try this (or study it first) approach by Spiegel123 AB forum user.

    We have time to time nice discussions at AB forums about similar issues with approaches. He (or She?) has develop an amazing combo based on AB3/AUM/LoopyHD/midi tools... to get more or less what you want and song parts with multiple midi output from one midi command (I'm supposing since I didn't look deep into it but it was what I was researching before I found GTL)

    The drawbacks in this option (and IMHO) are risks from too many things happening at once (and apps fighting for resources) something can go wrong and wreck the whole setup. If you are doing it at home it means restart and nothing else. If you are doing a gig this means you need a B-plan and lot of carisma to entertain until reboots happens. Not my cup of tea...

    Buy external hardware fx units and use it alongside GTL. In fact I have even external hardware looper to avoid carrying GTL to some kind of gigs where live looping isn't the main goal but backing tracks are the. Again it has to see with what's the main goal and how many risk you want to take against your crowd.

    Drawback: Money and learn a new hardware (I'm still understanding how my tc Helicon Perfom VK works and I still didn't loaded a full 5 song part into my digitech Trio+)

    Final thoughts
    I know this could sound discouraging but it's just my opinion (based on more than 18 years looping and dealing with all the traps) and my approach is JKD based (applied to Music as Artform) so I don't expect to nobody following me step by step but I hope some of my experience and applied knowledge help others in their paths.


  • I see that I forgot to answer you to your post, @dubbylabby.

    So thanks a lot for it. It is very valuable to receive feedback and suggestions from people who are much longer in the looper business than I am.

    All of your 3 suggestions are no real option for me. Buying Ableton and have a Macbook with me while traveling is definitely not what I want (I go traveling to leave everything related to working and computers at home, haha). The setup by Spiegel123 is very interesting and gives me some more ideas, but as I need the song structure thing, I will stick to GTL. And buying external hardware goes against my minimal-gear (and lightweight backpacker traveling) principles. :wink:

    I added another post, asking @Jack why GTL applies FX after recording loops:

    If this would be solved, I'd have everything I need, I guess. :smiley:

  • The AUM approach pointed is the middle-step between just GTL and Loopy multiouts... for me has the drawbacks of too many apps for live gigging but if it works for you, go for it!

    Btw I bought an rc505 (after selling the tc and the trio+) because Roland updated the firmware lomg ago adding something similar to song parts and the built in fx unit seems enough for my needs (maybe I will add another fx unit but still researching). Also I wonder about using zenbeats in junction (since Launchpad app only works with launch controllers...) and also wondering about adding an spds or similar...

    Cheers mate!

  • @dubbylabby said:
    The AUM approach pointed is the middle-step between just GTL and Loopy multiouts...

    Can you tell me a bit more about "Loopy multiouts"? :smile:

    At the time being, I would run AUM and GTL side by side, I won't need Audiobus AFAIK. Why's that "too many apps"?

  • Hi Josh,
    Please ask espiegel123 user at ABforums. I’m quiting social media ans that’s include that place.


  • Just wanted to point out that meanwhile I managed to implement something like this:

Sign In or Register to comment.