Flex Time algorithms and parameters in Logic Pro for iPad

Flex Time algorithms are track-based settings that determine how the timing or pitch of your audio material can be altered—using time compression or expansion, manipulating invisibly sliced segments, or speeding up or slowing down the material. You can choose an algorithm based on the type of audio material you’re working with. Each algorithm comes with its own individual parameters, located in the Track inspector below the Flex Mode parameter.

Figure. Track inspector showing the Flex settings.

Choose and adjust a Flex Time algorithm

Tap the track icon of the audio track you want to edit.
Tap the Inspector button in the view control bar or press I on your external keyboard to open the Track inspector.
In the inspector, tap the Level menu and choose Track.
Tap the Flex switch to turn on flex for the track.
The Flex Mode parameter and any additional settings are only displayed when the Flex switch is turned on.
Tap the Flex Mode pop-up menu and choose an option.
Adjust any of the additional flex parameters if necessary.

Note: Any audio region that has its Flex & Follow parameter set to Off in the Region inspector automatically changes to On when you enable flex on that track.

Use the Monophonic algorithm

In the Track inspector, tap the Flex switch to turn on flex, then tap the Flex Mode pop-up menu and choose Flex Time - Monophonic.
Monophonic is designed to be used on melodic instruments only playing a single note at a time, and is therefore good for solo vocals and monophonic solo instruments—melody and bass lines, for example. When you use this flex algorithm, your recording should be relatively dry, without audible reverberation. Otherwise, you may want to try using Polyphonic. Monophonic comes with a single parameter:
- Percussive: Preserves the area around transient markers to protect the percussive part of the sound. If selected, it allows better timing for all kinds of percussive monophonic tonal material, such as plucked strings (guitar, bass) or tonal percussion. If unselected, it prevents glitches on transient markers in nonpercussive tonal material, such as bowed strings or wind instruments.

Use the Slicing flex algorithm

In the Track inspector, tap the Flex switch to turn on flex, then tap the Flex Mode pop-up menu and choose Flex Time - Slicing.
Slicing cuts the audio material at transient markers, then shifts the audio while playing each slice at its original speed. No time compression or expansion is applied to the shifted audio. Any gaps that occur as a result of shifting the audio can be filled using the decay function. Slicing is a good choice for drums and percussion and comes with the following parameters:
- Fill Gaps: Turns the decay function on or off, allowing you to fill any gaps that occur between sounds as a result of shifting the audio.
- Decay: Sets the decay time between sounds because no time stretching takes place to compensate for the gaps.
- Slice Length: Shortens each slice by a percentage value. Shortening slices can be helpful for removing unwanted pre-attack sounds from the following slice, or to create a gated effect.

Use the Rhythmic flex algorithm

In the Track inspector, tap the Flex switch to turn on flex, then tap the Flex Mode pop-up menu and choose Flex Time - Rhythmic.
Rhythmic time stretches the material, looping audio between slices in order to fill any gaps. This algorithm is most suitable for material such as rhythmic guitars, keyboard parts, and Apple Loops. Rhythmic comes with the following parameters:
- Loop Length: Sets the length of the looped section at the end of a slice that is used for time expansion.
- Decay: Defines a decay value for the looped area.
- Loop Offset: Allows you to move the looped area up to 100 ms to the left, preventing pre-attack sounds from the following transient from appearing in the looped and crossfaded area.

Use the Polyphonic flex algorithm

In the Track inspector, tap the Flex switch to turn on flex, then tap the Flex Mode pop-up menu and choose Flex Time - Polyphonic.
Polyphonic time stretches material based on a process called phase vocoding—a process that uses phase information to time stretch an audio signal without touching its pitch. It is the most processor intensive of all the flex algorithms, but it delivers high sonic quality with suitable polyphonic material. It’s recommended for complex polyphonic material and is good for all kinds of chords—such as guitar, piano, and choir—and also complex mixes. Polyphonic comes with a single parameter:
- Complex: Activates more internal transients in the audio material.

Use the Speed (FX) flex algorithm

In the Track inspector, tap the Flex switch to turn on flex, then tap the Flex Mode pop-up menu and choose Flex Time - Speed (FX).
Speed time stretches material by playing the source material faster or slower, including pitch change. Because of the pitch shifting, this flex algorithm is mainly useful for percussive material, but it can be used on all material for interesting creative effects.

Use the Tempophone (FX) flex algorithm

In the Track inspector, tap the Flex switch to turn on flex, then tap the Flex Mode pop-up menu and choose Flex Time - Tempophone (FX).
Tempophone emulates the effect of a historical tape-based time-stretching device known as a tempophone, and results in a mechanical sound with many artifacts similar to those produced with granular synthesis techniques. Tempophone is intended to be used creatively for special effects and comes with the following parameters:
- Grain Size: Sets the size of the grains that are played or repeated in their original speed and crossfaded to create time compression or expansion.
- Crossfade: Adjusts the crossfade length from 0.00, which produces hard artifacts, to the full grain length of 1.00, which tends to sound softer.

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