Logic Question

[guitarose]

In Logic, is it possible to trigger a midi track using a volume envelope on an audio track, so that it gets triggered when it reaches a certain volume level?

So for example, could I hook up a midi sound to be triggered by an audio drum beat crossing the envelope threshold?

...if so, how?

[wren]

Seems to me that the easiest thing to do would be to use a gate.

See here: Noise gate (http://en.wikipedia.org/wiki/Noise_gate); see paragraphs 6 and 7.

[iaresee]

You can use the Beat Mapping Track to assign midi events to key audio events in an audio stream. It's got an algorithm that's more complex than just a envelope detector. If you have Orren Merton's Logic Pro 8 Power! it's pp. 112 - 121. In the Logic Pro help search for "beat mapping" and you'll get a bunch of hits. You want the "Beat Mapping With Audio Regions" section -- it starts on p 658 (Chapter 31) in the Logic Pro manual. The book's description is much better IMO.

[guitarose]

Cool. Thanks. I don't really know what beat-mapping is, but I'll look into it. More reading, but thanks for the pointer.

[iaresee]

Cool. Thanks. I don't really know what beat-mapping is, but I'll look into it. More reading, but thanks for the pointer.

It detects peaks in an audio stream and maps the peaks to MIDI notes. It even maps the velocity, attack and decay. Very nice for replacing drums or over dubbing electronic kits on analog grooves.

[guitarose]

Sounds cool. I'm more interested in layering sounds than replacing, but looks like a good system..

Though it's called beat mapping - does it only work for beats? or could I map a guitar part to trigger a synth (for example)?

[Rents]

unsure about live, yes maybe use a noise gate to trigger something, there'd be a way to set it up in the enviroment section

otherwise, you can extrapolate midi groove templates and gate information from audio tracks, but this is in retrospect rather than on the fly

in logic 7 these options are both available when you double click on the audio region and there in one of the dro down menus.

what kind of midi do you want to trigger?

if it were some sort of pad or something - you could have it constanly playing and sidechain to live audio track?

[iaresee]

Sounds cool. I'm more interested in layering sounds than replacing, but looks like a good system..
You can use it for layering too. It's just often used for drum sound replacement.

Though it's called beat mapping - does it only work for beats? or could I map a guitar part to trigger a synth (for example)?
The input waveform can come from any instrument. I'll admit I've only tried it with drum beats. The resulting MIDI can trigger anything you like.