Alchemy for Creative Loop Manipulation

Alchemy For Creative Loop Manipulation

Alchemy supports the playback of Apple Loops as well as standard .wav audio les and
can manipulate tempo and pitch in realtime. Alchemy’s sophisticated synthesis engine
can transform loops with multiple forms of re-synthesis and an abundant collection of
filters, modulation and effects racks. This white paper introduces some of these new
features.
Overview

Alchemy can generate a synthesized version of an audio file using a process called
resynthesis. This expands the creative options for manipulating the sound. One of those
options is the ability to time stretch and pitch transpose the sound in realtime. The following
steps show how to use the Speed and Position controls for that purpose.

1. Select an audio loop
To control tempo, you will need to know the length of your loop in bars/beats. If it’s an Apple Loop, the
number of beats are listed right within the loop browser. This tutorial uses an Apple Loop, but any
supported file format will work just as well. Before continuing on, set your project tempo to 110 BPM.
Open the Apple Loops browser in Logic by clicking the loop browser icon in the control bar. Use the search
field and type “Basic Vintage Break.” If you look in the browser you can see the original tempo is 100
BPM, its 8 beats (2 bars) long.
2. Open Alchemy and switch to Advanced view

3. Clear Settings from Alchemy’s File menu. This resets Alchemy’s settings and makes it easier to build
sounds from scratch.
4.Select Source A Editor
Click the A tab in the source section. This displays the detailed edit controls for Source A.

5. Open Import Audio Window
Click on the waveform / import audio menu and select “Import Audio”

6. Add Apple Loop
Drag “Vintage Funk Loop 03” from the Apple Loops browser and drop it onto the Alchemy file browser area
labeled Drop Zone. It’s important to note that when you import audio, you must select the Analysis Mode which
corresponds to the synthesis engine you plan to use. The choice you make here cannot be altered without
repeating the import process.
Choosing the synthesis method most suitable for this type of material is key to getting good results. For this
tutorial, you will use Spectral and Formant. Spectral is ideal for a wide range of source material from
polyphonic melodic recordings to drums and percussion. Alchemy’s high quality Spectral engine is especially
good at preserving transients making it useful for drums and percussion. The Formant option extracts the
resonances from the original audio and converts into a lter shape which can be edited and reshaped.

Set the Analysis Mode to Spectral + Formant.
Click the Import button in the lower right corner to begin analysis and import the loop into Source A.
Once Alchemy has completed the analysis, try playing some notes on your controller keyboard. You will
hear the loop play at its original recorded speed if you play C3, but playing at other pitches transposes the
sound while playing at a fixed tempo. To make this loop play at the current session tempo, we need to
control of playback speed.

7. Set Speed to Zero
Set the Speed knob to 0%. This stops the loop from playing forward in time and will repeat the
rst few samples at the current position.
Try holding down a note and listen to how you can take control of the playback using the Position
knob. This moves playback forwards and backwards through the loop. Set the value to 0% before
moving to Step 8.

8. Add LFO to modulate the Position knob
You will now use an LFO to move the Position knob through the loop sync’d to the project’s tempo.
Right click on the Position knob and select Add Modulation > LFO1. This assigns an LFO to control the
Position knob.

9. Setup LFO
The modulation section in the middle of Alchemy will now display the controls for LFO 1. Switch the LFO’s
shape from Sine to Ramp Up and set the rate to 2 (measures) to match the length of the Apple Loop. Click the
Bipolar button to turn it off. Note When Bipolar is active, the LFO outputs both negative and positive values in
each cycle (from -50% to 50%). When off, only positive values are output (from 0% to 100%). If you play and
hold a note on your keyboard, you can see a small dot around the Position knob indicating its values changing
from 0% to 100%. Bipolar is useful for controlling parameters like pan where 0 is in the midpoint of the knob’s
rotation and you want the value to oscillate around the centre.
Triggering C3 should now play the loop at its native pitch but the tempo should now match the project.

Explore these additional steps after completing the tutorial.
• LFO Trigger Mode on/off
If you turn off the Trigger mode, you will notice that the loop position continues to move through the file but is
only audible when you play a note. This allows you to create gating and stuttering effects by rhythmically
triggering notes. Try playing a series of very short 8th notes over this loop to change its feel.
• Pitch Bend Range
Its also fun to play notes of di erent pitches or even pitch bend to add that chopped & screwed e ect to your
loops. The default pitch bend range is only 2 semitones, but Alchemy supports pitch bends of up to 36
semitones up and down. To set this, switch away from Source A to the Global view. In the Voices section,
you can set the up and down pitch bend values independently.

• Set LFO Shape to Ramp Down
Changing the LFO shape to Ramp Down plays the loop backwards by starting the Position at
100% and moving back to 0%.

• Replace LFO with MSEG envelope
The MSEG envelope can duplicate the same kind of looping Ramp Up pattern used in the LFO example
above but are capable of longer more complex patterns than a repeating ramp. MSEG envelopes are useful
when you have specific ideas about how you want parameters to change over time. MSEG are capable of
creating a range of modulation patterns from simple short ramps to very long, complex sequences.
For example, here’s an 8 bar, complex rhythmic pattern:
In this next tutorial, we’re going to use the MSEG envelope to take creative control over the Position knob
just like we did with the LFO in the above tutorial. This time we will use the MSEG to move play Position to
the halfway point of the loop, play in reverse, then forwards again all while following the tempo.

1.Disable the LFO
Select the Position knob and then click the button next to the modulation area to disable the LFO. If you
play notes now, it no longer plays forward through the loop.

2.Add MSEG to control the Position knob
Right click on the position knob and select MSEG Envelope 1

3.Setup MSEG Envelope 1
Click the File button in the MSEG editor and load the preset “Ramp Up”. This preset
creates a 8 beat (2 bar) ramp from 0% to 100%. So, if you play a note, the result is just
as it was when we used the LFO in the above example.
The exact position of each point in the MSEG are important to keeping consistent tempo. To add points, just
click anywhere along the graph line. If you add one by mistake, double click on a point to remove it.
As you move points, they will snap to the tempo grid. Add a point midway at beat 5 and drag up/down until
the Y value reads 50%. Add another point at beat 7 and drag it down until the Y value reads 25%. Move one
of the points at beat 9 down until the Y value reads 50%. Double click the mouse to remove the last point.
The final MSEG graph should look like this image. The red circles are added to show you the value required
for each point.

Try holding a note down and it should play forwards, backwards and then forwards again all
while locking in time with the project tempo. More complex use of this can cause the position
to jump to specific places within the loop to make variations of the original loop.

References
Taken from a white paper called, ‘Logic Pro X, Alchemy For Creative Loop Manipulation’. Located at,
https://www.apple.com/logic-pro/docs/alchemy_for_creative_loop_manipulation_0818.pdf. Retrieved
August 2015

Alchemy for Creative Loop Manipulation

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