Manipulate loops in Alchemy in Logic Pro for Mac

Logic Pro provides great options for working with loops and Apple Loops on tracks. If you want to trigger loops live, or shape them with synthesis tools, you can do so using Sampler, Ultrabeat, and Alchemy. Alchemy supports playback of Apple Loops as well as .aif, .caf, and .wav audio files, and you can use it to manipulate tempo and pitch in real time. Alchemy’s sophisticated synthesis engines can transform loops with multiple forms of resynthesis and extensive filter, modulation, and effects options.

Note: Images shown are not specific to the presets used in tasks. They are included as a guide to help you find areas and parameters in the Alchemy interface.

Time stretch and pitch shift samples in real time in Alchemy

If you can’t find the loop used for this example, you need to download additional content packages. To do so, choose Sound Library > Open Sound Library Manager from the Logic Pro menu, then download the missing content.

In Alchemy in Logic Pro, click the File button in the Name bar and choose Initialize Preset from the pop-up menu to reset all Alchemy parameters to default settings.
Important: Use of Initialize Preset automatically turns on wide unison mode. See Alchemy wide unison mode.
Set the project tempo to 110 BPM.
Click the source select field for source A, and choose Import Audio from the pop-up menu.
The Import window opens.
Open the Apple Loops browser, and type “Basic Vintage Break” in the search field. Drag the Vintage Funk Loop 03 file from the Apple Loops browser to the Dropzone area of the Import window.
Note that the original tempo of this file is 100 BPM and that it is 8 beats (2 bars) long.
Click the Spectral and Formant analysis mode buttons at the lower left, then click the Import button.
This determines the synthesis engine used for resynthesis of the audio sample. Spectral + Formant is a good general purpose option that works well for drum loops. It’s also the default setting in a new instance of Alchemy. When analysis is complete, you can trigger the loop at its native pitch and speed by playing C3 on your keyboard. Playing other pitches transposes the loop, but retains the tempo.
Set the Speed knob in the source main controls section to zero percent (full left).
This stops the loop from playing forward in time and repeats the first few samples at the current position.
Hold a note and rotate the Position knob to hear how playback is affected.
The Position knob moves playback forward and backward through the loop. Set the value to zero percent (full left).

Modulate position with an LFO in Alchemy

In Alchemy in Logic Pro, Control-click the Position knob and choose Add Modulation > LFO > LFO1 from the shortcut menu.
This assigns LFO 1 to control the Position knob, and the central modulation section automatically updates to display the controls for LFO 1.
Switch the LFO shape from Sine to Ramp Up, and set the Rate to 2 (measures) to match the length of the Apple Loop.
Tip: Changing the LFO shape to Ramp Down plays the loop backward by starting the Position at 100% and moving back to 0%.
Click the Bipolar button to turn it off.
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, a small dot around the Position knob indicates 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 center.
Play C3 to hear the loop at its native pitch but at a tempo that matches the project (110 BPM).

Explore further loop manipulation options in Alchemy

In Alchemy in Logic Pro, explore these additional options with the same loop to get a feel for Alchemy’s loop manipulation capabilities.

Turn off Trigger mode to hear the loop position continue to move through the file only 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.
You can play notes of different pitches or can use pitch bend to add a chopped and screwed effect to your loops. The default pitch bend range is 2 semitones, but Alchemy supports bi-directional pitch bends of up to 36 semitones. To set this, click the Global view button and set the up and down pitch bend values independently in the master section.

Modulate position with an MSEG in Alchemy

The MSEG envelope can duplicate the same kind of looping Ramp Up pattern used in the LFO task but is capable of longer, more complex patterns than a simple repeating ramp. MSEG envelopes are useful when you have specific ideas about how you want parameters to change over time. MSEG modulators are capable of creating a range of patterns from simple short ramps to very long, complex sequences.

In Alchemy in Logic Pro, click the Position knob, then click the button next to the modulation area to disable the LFO.
Play a few notes and you will hear that the loop no longer plays forward.
Control-click the Position knob, and choose Add Modulation > MSEG Env > MSEG1 from the shortcut menu.
This assigns MSEG 1 to control the Position knob. The central modulation section automatically updates to display the controls for MSEG 1.
Click the File button in the MSEG editor, and load the Ramp Up preset.
This creates an 8 beat (2 bar) ramp from 0% to 100%. When you play a note, the result is identical to that of the LFO modulation used in the previous task.
Click along the graph line in the MSEG editor to add three points near bars 5, 7, and 9. Double-click a point to remove it.
Note: The exact position of each point in the MSEG is important for keeping a consistent tempo.
Drag points horizontally to move them, noting that they snap to the tempo grid. Drag vertically to set the following values for each point.
- Bar 1: Point value 0%
- Bar 5: Point value 50%
- Bar 7: Point value 25%
- Bar 9: Point value 50%
Hold a note to hear the loop play forward, backward, and then forward again at the project tempo.
More complex MSEG settings can cause the position to jump to specific points in the loop, thus creating variations of the original loop.

Download the guides:

Logic Pro User Guide: PDF

Logic Pro Instruments: PDF

Logic Pro Effects: PDF

Control Surfaces Support Guide: PDF

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Logic Pro User Guide for Mac

Manipulate loops in Alchemy in Logic Pro for Mac

Time stretch and pitch shift samples in real time in Alchemy

Modulate position with an LFO in Alchemy

Explore further loop manipulation options in Alchemy

Modulate position with an MSEG in Alchemy