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  • Nicywuo
    Posts: 17
    Joined: Dec 11th, 2009, 02:14
    MIDI LFO to control faders, etc.
    For awhile I have wanted to be able to use an LFO to control plugin parameters. I got the idea from adding parameter behaviors in Motion. Seems like it would be a nice addition to Logic! I tried to make an LFO in the environment several times and couldn't figure it out. When I found the MIDI LFO from swiftkick.com, created by Len Sasso, I was pretty stoked. But I couldn't get it to work. Then I found this thread on Logic Pro Help: http://www.logicprohelp.com/viewtopic.php?t=26896 Someone has updated it to work with Logic 9! Once I downloaded this, I was able to import it in to a project, cable it to a transformer, and then convert it in to fader data (as I learned how to do from Rounik's Randomizer TNT). This can then be cabled to a channel strip, and there it is! I've been having loads of fun with it. It's great but I can't figure out how to control the amplitude of the wave. So right now when ever I assign it to something, I'm getting the full range of the parameter (if it goes as high as 127). I was able to limit it with a transformer, but that creates some weird rhythmic things as the parameter assigned to it will just stop at that number and wait for the wave to come around to turn it back down. So it's not quite as useful as it could be. I opened up the macro to see if I could tweak it in there, and realized immediately that I am a long way from truly understanding the environment. Len Sasso is a very smart man. Anyway, this has been a project of mine half just to learn a bit about the environment, but any help on tweaking this last part would be very appreciated. Thanks! Bret PS: Another interesting part of this might be that there seems to be a fader missing at the bottom right when compared to the image on the above linked site.
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  • Peter Schwartz
    Posts: 545
    Joined: Sep 15th, 2007, 06:04
    Re: MIDI LFO to control faders, etc.
    Changing the LFO's amplitude, so to speak, can only be accomplished by altering the second data byte values of the output. If those values are 0 - 127, then reducing the amplitude is a matter of [i]scaling[/i] those values by running the data into a transformer and using the scale function. The more you scale the values, the more you're going to create a very stair-stepped waveform shape from the LFO. But there's more... Simply scaling the second data byte values is going to affect the higher values more than it will lower ones. That means that your modulation data will end up being weighted more towards the low end of whatever parameter you're modulating as opposed to reducing the scale on both sides of "center" (value of 63 or 64). For example, if your LFO is causing an EQ band to vary between -24 and +24, by simply scaling the values you're going to end up with less modulation from 0 to +24 and the same amount of modulation from 0 to -24. If that's a concern, post back, and I'll elaborate on how to create a scaler that will reduce both the high and low values simultaneously.
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  • Nicywuo
    Posts: 17
    Joined: Dec 11th, 2009, 02:14
    Re: MIDI LFO to control faders, etc.
    Thanks so much for getting back! I don't think the scaling thing will be too much of a problem for what I'm keen on using it for, but how do I scale the wave? I tried putting a transformer after it and scaling byte 2 but it didn't work right. Maybe I don't totally understand how the scale function works. Do I need to open up the macro and find an output there? If so, what should I look for? Thanks again for the help here. Bret
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  • Peter Schwartz
    Posts: 545
    Joined: Sep 15th, 2007, 06:04
    Re: MIDI LFO to control faders, etc.
    Couple of things... I took a look at the "GUI" of Len's LFO and I see that there's a scaling parameter, as well as an offset parameters. Just curious to know if you've experimented with those at all. On another front... I don't have time to take that environment apart, but I can still help you with understanding how things work. First, a few questions... 1) what kind of events is the LFO generating? 2) what are you using it to modulate? Now some comments... The LFO isn't actually outputting a wave so much as it's outputting a repeating sequence of values. Without any offset or scaling, those values will range from 0 - 127. An approximation of a triangle waveshape is when the values count from 0 to 127, then fall from 126 - 1, then rise again from 0 - 127, and so on. Let's say you're modulating an EQ band's cut/boost, as I described in my previous post. A value of 63 (or 64 -- sorry, not in front of Logic right now) from the LFO is going to set the cut/boost to a value of zero as seen on the EQ. So here, the LFO's output value of 63/64 is the "center" value. Values above that will create an EQ boost, and values below that will create an EQ cut. So even though the LFO's values are all positive numbers (or zero), they create both positive and negative changes to the EQ band's cut/boost. Therefore, the LFO is acting in a "bipolar" fashion with respect to the values seen in the EQ band. In other words, a string of positive numbers, rising and falling between 0 and 127, are going to cause both positive and negative changes to the EQ's cut/boost parameter. If you wanted to make the LFO cause the EQ band to only swing between 0 and +24 (boost), you'd want the LFO to only output values between 63/64 and 127. Conversely, if you wanted the LFO to cause a cut-only action, it would have to output values between 63/64 and zero. In both cases, the LFO would be acting in "unipolar" fashion. Before I go on further, let me know if you understand that bit of the theory so far.
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  • Nicywuo
    Posts: 17
    Joined: Dec 11th, 2009, 02:14
    Re: MIDI LFO to control faders, etc.
    Thanks, Ski! So, I read your post about 6 times and it started to make sense. For some reason I still can't get the scale function to work. But setting the range does help things, although it's not perfect. Before you spend any more time on me (and thanks again for doing so), I'm going to watch your MIDI demystified tuts (I started last night), and Martin's Logic Environment Explored. I didn't realize that that one existed because it is buried back in the Logic 6 section. :) Once I finish these, I'll post again. It's easier for me to learn stuff when I have a goal in mind, so that's all this LFO stuff has been for me. So if it doesn't work out, that's alright. You've already increased my knowledge 10 fold. Steve H talks about the channel strip as being "one big synth." I love using the bit crusher as part of my one big synth. So wouldn't it be great if I could give an envelope to downsampling, or assign a LFO to it? Or maybe the brake/tremolo stuff on the Rotor plugin? Rounik's randomizer comes in very handy for some of this idea, but an LFO would allow me to create rhythmic patterns to the sound. Once again, thanks. Having someone of your expertise answer these comments is not something I take for granted. Bret
    Reply
  • Peter Schwartz
    Posts: 545
    Joined: Sep 15th, 2007, 06:04
    Re: MIDI LFO to control faders, etc.
    Hi Bret, Thanks for your very kind reply! The biggest problem you'll face trying to use an environment-generated LFO is that it won't always act (or create a sonic result) like that of a synth's LFO. This is because we're dealing with a limitation in the [i]resolution[/i] of the LFO. As you'll learn in the MIDI Demystified tutorial, MIDI values typically range from 0 - 127 (and the same is true of Logic's fader events, the very MIDI-like that's generated when you move various controls on Logic plugins, synths, etc.). 0 - 127 = 128 steps. By itself that's not a lot of [i]resolution[/i] (the number of values that you have at our disposal to change a plugin parameter with). When you try to scale back that range of values so that they don't modulate a plugin parameter between its extreme settings (such as sweeping the full -24/+24 range in an EQ band), the only choice you have is to narrow the range of values feeding the plugin so that the parameter doesn't swing to those extremes. Now, the sound of the EQ cutting/boosting that amount based on the 128 values of the LFO might sound somewhat smooth. But let's say you only want to have the EQ swing between -5 and 0 dB, and to get the result you want, the range of LFO values has to be narrowed to rise and fall between [b]57[/b] (-3 dB) and [b]64[/b] (0 dB). (BTW, these numbers are for example only and may not reflect the actual values required). So... [b]57 - 64[/b] is only eight values, and so the transition from no cut (0dB) to that -3 dB cut is going to step with each value, meaning that you'll likely hear a distinct "jump" in the sound as the values change instead of a smooth transition in the sound as the values change. Whew! Anyway, do post back when you want to continue the conversation. I'll look forward to your reply, whenever that is! And I hope you enjoy MIDI Demystified.
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