Quick wins for a faster PC:
Repair Windows errors before they cause bigger problemsFix Now →Scan for outdated or missing drivers - takes under a minuteDriver Scan →Clear out junk files and repair common Windows errorsFree Scan →iTechGuides is reader-supported. When you buy through links on our site, we may earn an affiliate commission. As an Amazon Associate I earn from qualifying purchases. Learn more
If a synth evaluates its LFO only once per host audio block, the LFO’s modulation updates at the block rate—not continuously at the audio sample rate. In that implementation, changing the host buffer size changes the control signal’s sampling rate and can make a fast LFO fold to a lower frequency. This is a property of the audited code path, not a rule that applies to every synthesizer.
What it means for an LFO to run at the buffer size
Let fs be the audio sample rate and N the number of audio samples in a host block. If the code computes one LFO value per block, it produces fs/N modulation values per second. The control sequence’s Nyquist limit is half that rate: fs/(2N).
A requested LFO frequency above this limit cannot be represented faithfully in the block-by-block sequence. It aliases, or folds, to a different frequency. The LFO may still advance its phase by the intended amount over each block, but that does not make the waveform continuously evaluated: if sin() is called only once per block, the destination still receives only one new modulation value per block.
Do these 3 things before closing this tab:
1Scan for outdated or missing drivers - takes under a minute2Clear out junk files and repair common Windows errors3Fix the driver behind crashes, sound loss and screen glitchesHow buffer size changes the result
Lluis Estape’s article describes this behavior in its own synth implementation and reports FFT measurements of the resulting modulation sequence. At 44.1 kHz, the figures change substantially with block size:
#1 Best Overall
- Next-Gen Music Production and Beat Maker Essential - USB-powered MIDI keyboard controller with 25 mini velocity-sensitive keys, optimized for studio or beat production, piano-style performance, synth leads, sample triggering
- Real-Time Control and Navigation - 8x assignable 360° knobs, a vibrant full-color screen and push/turn encoder for hands-on access to settings, presets, and DAW functions, without reaching for a computer
- Iconic MPC Pads with RGB Feedback - 8 velocity- and pressure-sensitive MPC pads deliver an iconic finger-drumming experience, plus dynamic visual feedback to match your performance in studio or on the go
- Studio Instrument Collection Included - A powerful VST/AU and standalone virtual suite packing 1000+ pro-grade drums, keys, synths, bass, FX from AIR, Akai Pro and Moog, plus MPK Mini IV integrated controls
- Pre-Mapped DAW Integration - Get producing in under 15 minutes with Ableton Live Lite 12, Logic Pro, FL Studio and more; comes with an expanded DAW-mapped transport section for uninterrupted workflow
| Host block size | Control update rate | Control Nyquist limit | Reported result for a 20 Hz LFO |
|---|---|---|---|
| 2048 samples | About 21.5 updates per second | About 10.8 Hz | Estape reports the 20 Hz setting folding to 1.5 Hz in an FFT measurement. |
| 1024 samples | About 43.1 updates per second | About 21.5 Hz | Estape reports the setting near 20.03 Hz. |
These values are for the article’s described code and measurements, not a general benchmark. At the larger block size, the 20 Hz request is above the control signal’s roughly 10.8 Hz Nyquist limit. At 1024 samples it sits below the roughly 21.5 Hz limit, so the reported sequence stays near the requested rate.
Changing the audio buffer size can therefore change the audible modulation in this design even when the sample rate and LFO setting stay fixed. That is the useful diagnostic clue: if a plugin’s modulation speed changes with host block size, inspect how often it evaluates the modulation waveform and updates its destination.
Rank #2
- 61 key keyboard piano kit: complete beginner set with stand, bench, headphones and note stickers.
- Expressive playing: pitch bend wheel and LED panel with 200 rhythms, 200 tones and demo songs.
- Learn faster: Simply Piano lessons and keynote stickers guide kids and adults note by note.
- Quiet practice: headphones keep sessions private in shared rooms and family spaces.
- Everything included: start playing on day one with fewer extra purchases.
How to audit an LFO’s control rate
- Find the waveform evaluation. Trace the code that computes the LFO value, such as a call to
sin(), and determine whether it runs once per host block, once per sub-block, or once per audio sample. - Count destination updates. Check how many distinct LFO values reach the modulated parameter during one audio block. A correct phase increment does not establish that the destination is updated at audio rate.
- Calculate the limits. For a block-sampled value, divide the audio sample rate by the block size to get the control update rate, then divide that result by two for its Nyquist limit.
- Compare buffer sizes. At the same sample rate and requested LFO frequency, test more than one host block size. Compare the modulation sequence or its FFT with the calculated update rate and Nyquist limit.
Estape reports reproducing the code in float32 and measuring the sequence with an FFT. The measurements above are his reported results; they are not an independent reproduction.
Why phase bookkeeping alone does not solve it
In the audited implementation, phase advances using the requested rate and the block duration—equivalent to rate multiplied by N/fs. That can preserve the intended phase progression from one block to the next. But a destination receiving only one sine value per block sees a sampled control sequence, whose usable frequency range is limited by the block-rate Nyquist frequency.
Rank #3
- Full Creative Control - A dynamic 37-Key MPK Mini keybed for 3 full octaves of melodic and harmonic performance; Easily connect to your DAW or studio equipment with the USB-powered MIDI Controller
- Advanced Connectivity - Connect to different sound sources with CV/Gate and MIDI I/O; Control modular gear, sound modules, synthesizers, and more to bring new sound sources into your music production
- Native Kontrol Standard (NKS) Integration - Akai Professional and Native Instruments have partnered to bring NKS support to the MPK Controller series, get ready to Kontrol straight from your MPK
- Choose Your Exclusive Complimentary NKS Bundle - Browse and control Native Instruments presets and sound libraries; select one of three curated Komplete 15 Select bundles: Beats, Band, or Electronic
- Record and Compose Without a Computer - Connect to your production station and use the built-in 64-step sequencer featuring one track for drums and one for melodies or chords, with up to 8 notes each
Estape summarizes the consequence: “A modulation source that can be set faster than the control Nyquist does not run fast: it folds, exactly like an oscillator above half the sample rate, for exactly the same reason.” The key distinction is between how phase is advanced and how often the waveform is evaluated and delivered.
A fixed sub-block update can decouple control from the host block
One remedy in the demonstrated implementation is to split each host block into chunks of up to 32 samples. Advance the LFO phase by each chunk’s duration and render the synth in the corresponding segment. The LFO then updates at the sub-block rate rather than only at the outer host-block boundary.
Rank #4
- Music Production and Beat Maker Essential -USB powered MIDI controller with 25 mini MIDI keyboard velocity-sensitive keys for studio production, virtual synthesizer control and beat production
- Total Control of your Production - Innovative 4-way thumbstick for dynamic pitch and modulation control, plus a built-in arpeggiator with adjustable resolution, range and modes
- Native Kontrol Standard (NKS) Integration - Akai Professional and Native Instruments have partnered to bring NKS support to the MPK Controller series, get ready to Kontrol straight from your MPK
- Choose Your Exclusive Complimentary NKS Bundle - Browse and control Native Instruments presets and sound libraries; select one of three curated Komplete 15 Select bundles: Beats, Band, or Electronic
- The MPC Experience - 8 backlit velocity-sensitive MPC-style MIDI beat pads with Note Repeat and Full Level for programming drums, triggering samples and controlling virtual synthesizer / DAW controls
At 44.1 kHz, a 32-sample chunk yields 44,100/32 = 1,378.125 control updates per second and a Nyquist limit of 689.0625 Hz. Estape rounds those figures to 1,378 updates per second and 689 Hz. That is ample for the example’s maximum requested LFO rate of 20 Hz.
The 32-sample size is a design choice for this implementation, not a universal optimum. A synth supporting faster modulators needs a sufficiently high update rate or sample-rate processing. The code also needs robust phase wrapping: subtracting floor(phase) wraps the phase even when an increment exceeds one cycle, unlike a single conditional subtraction.
Best Value
- UNLIMITED CONNECTION: This true full size 61 key keyboard piano is made of premium material. The LCD display can simply and clearly displays the status of the functions being used. With audio input/output/microphone jack(with UDISK port),you can connect microphone and headphone(included), you will not interfere with others when practicing singing and playing late at night, fully enjoy the music
- TIMBRE AND RHYTHM: JIKADA 61-key electronic music keyboard has two built-in stereo speakers, provide 255 tones, 255 rhythms, 50 demo songs and 61 types of keyboard percussion and give you premium sounds and effects. With status memory function, you can save the tone, rhythm, tempo and other parameters to be changed during playing, for fast shifting
- 3 TEACHING MODES: JIKADA 61 light-up keys keyboard piano with 3 powerful teaching modes, lead you to step by step. And piano note stickers help you more easily to learn and memorize the music theory, musical notations and keys positions
- MULTI FUNCTIONS: This electronic keyboard has master volume/ accom volume/ tempo control, single-finger chords, fingered chords, sustain, vibrato, split, transposition, metronome, volume or transpose control. With record and playback function, and the playback function can also help the performer recall the performance effect and make targeted connections to improve the performance next time
- SUPER BUNDLE: Includes a keyboard (size: 36.4in * 13.4in * 3.5in), a x-shaped stand, a soft stool, headphones, a microphone, a music rest and a power adapter. And the stool can be folded for convenient storage and space-saving. This item is not intended for users under 12 years old
Smoothing is not a substitute for a sufficient update rate
Smoothing can soften abrupt steps in a modulation path, but it cannot recover a frequency that has already aliased. Estape reports that the cutoff modulation in the example sounded smooth while running at the wrong frequency. Treat smoothing and control-rate selection as separate decisions: one shapes transitions, while the other determines how often the modulation signal is sampled.
Not every synth LFO uses the host block rate
LFO behavior is implementation- and product-specific. For example, Ableton’s Live 12 documentation describes Operator’s LFO running at audio rates, where it can act as an additional oscillator. Ableton’s Live 12 Audio Effect Reference documents effect LFO time modes, tempo-synchronized divisions, quantization, and smoothing. Native Instruments’ Massive X manual distinguishes Free, Sync, and Osc modes; it gives Free mode a range of 0.004 Hz to approximately 60 Hz.
Those examples are not a universal standard. When comparing LFOs, check the update rate, its limit relative to the applicable Nyquist frequency, whether the rate is free-running or tempo-synchronized, and whether the modulator can enter audio-rate or oscillator behavior.
Quick Recap
- Lluis Estape, “Your LFO runs at the buffer size: auditing the control rate of my own synth” — implementation, calculations, and reported FFT measurements.
- Ableton Live 12 Instrument Reference — Operator LFO behavior.
- Ableton Live 12 Audio Effect Reference — effect LFO modes and behavior.
- Native Instruments Massive X Modulators manual — Free, Sync, and Osc modes.
Product prices and availability are accurate as of the date/time indicated and are subject to change. Any price and availability information displayed on Amazon at the time of purchase will apply.
