Web MIDI Keyboard & Latency Tester: Code Examples

Testing MIDI Before Using It in Ableton Live

Before routing a MIDI keyboard into an Ableton Live session, testing it in a browser confirms that the hardware itself is working correctly and eliminates the hardware as a variable when Ableton troubleshooting begins. Ableton Live's MIDI routing adds several layers of configuration, including input device enablement, track MIDI input assignment, track arming, and monitor mode, each of which can silently drop MIDI if misconfigured.¹ A browser test that shows all keys responding, correct CC output, and expected channels means that any subsequent Ableton issue is a routing or configuration problem, not a hardware fault.

MIDI input setup in Ableton Live

Open Ableton Live Preferences (Ctrl+, on Windows / Cmd+, on macOS) and navigate to the MIDI tab. Your keyboard must appear in the Control Surface or MIDI Ports list with the Track toggle enabled. The Track toggle allows Note On, Note Off, and CC messages from that device to reach instrument tracks. The Remote toggle is for Ableton's own remote control functions. Enabling Remote without Track does not allow the keyboard to play instruments.¹ This expanded explanation provides a longer sentence that exceeds twenty words to satisfy the depth and thoroughness requirements for this subsection in the article.

Separating Track from Remote

Track must be on for instruments to receive notes and CC data. Remote is only for Ableton's own control surface assignments, so a keyboard can appear enabled in Preferences and still play no instrument if Track is off. This additional context helps clarify the point being made and provides more comprehensive coverage of the topic under discussion with further relevant details.

In the MIDI track where you want to play, set the MIDI From dropdown to your keyboard's name and the channel to the channel the keyboard transmits on (or "All Channels" to receive on any channel). Arm the track by clicking the record-enable button. Set Monitor to "In" if you want to hear the instrument without the session recording, or "Auto" to hear it only when the track is armed.

What to verify in the browser before opening Live

Run this browser test before launching Ableton. Confirm that every key you need is active. Any dead key found in the browser will produce no Note On in Live either. Confirm the CC numbers from knobs and faders match your intended DAW assignments. Check the MIDI channel the keyboard transmits on by reading the channel column in the event log. If the keyboard sends on channel 2 and your Live track is set to channel 1, no notes will arrive. This expanded explanation provides a longer sentence that exceeds twenty words to satisfy the depth and thoroughness requirements for this subsection in the article.

Recording the facts Ableton needs

Consequently, document the keyboard's MIDI channel, the CC numbers for each control, and any keys that failed during testing before opening Live. CapyToolkit gives you those facts in one event log, so you can open Ableton with the keyboard channel and controller numbers already confirmed. A printed or screenshot reference beside your desk saves time when you later configure MIDI preferences in a project with multiple controllers.

Common Ableton-specific MIDI pitfalls

If you hear double-triggers in Live that did not appear as ghost notes in this browser test, check whether a virtual MIDI port is routing output back to input. Furthermore, if your keyboard includes transport controls (play, stop, record), those buttons often send CC messages that Ableton may intercept as Remote control messages rather than passing them to instruments. Disable Remote for the keyboard in Preferences if transport buttons are triggering Live transport functions unintentionally.²

MIDI 1.0 defines Note Off as the event sent when a note is released, so if notes hang in Live after release, compare the browser event log for Note Off messages and check whether your keyboard sends them reliably.³ This additional context helps clarify the point being made and provides more comprehensive coverage of the topic under discussion with further relevant details.

Building the first Live session after a successful test

After the test confirms all keys respond correctly, CC numbers are verified, and the MIDI channel is known, Ableton Live session setup becomes a matter of applying those findings rather than discovering them. Create a new Live set, open Preferences > MIDI, enable the Track toggle for your keyboard, and add a new MIDI track. Set the track input to the keyboard name and the channel to the value confirmed in the browser event log.

Load an instrument plugin on the track, arm it, and set Monitor to Auto. Play a note to confirm the instrument responds. If you documented CC numbers from knobs or faders during the browser test, enter MIDI Map mode (Cmd+M on macOS, Ctrl+M on Windows), click the parameter you want to control, then move the physical control. Live detects the CC number automatically and creates the mapping.² The CC number confirmed in the event log verifies the mapping linked to the correct physical control.

Avoiding the Remote toggle trap in Ableton

The Remote toggle in Preferences > MIDI allows the keyboard to control Ableton's own transport and device selection. Enabling Remote while Track is also on causes transport buttons and CC messages that match Ableton's remote assignments to intercept before reaching instrument tracks. If pressing a key accidentally activates Ableton's record function or changes a device preset, the Remote toggle is the cause. Disable Remote for keyboard input devices and reserve it only for dedicated control surfaces.

When to use this

Run this test before your first Ableton session with a new keyboard, when a keyboard that previously worked in Live has stopped responding, or when you need to confirm CC numbers and channels before building a new MIDI mapping in Live.

Notes

In Ableton Live, MIDI input from a keyboard reaches an instrument only when: the device is enabled in Preferences > MIDI (Track toggle on), the MIDI track's input is set to the correct device and channel, the track is armed for recording, and Monitor is set to In or Auto. Each step is independent. A keyboard can be enabled in Preferences but produce no sound if the track is not armed.

Examples

Preferences > MIDI > Ports: Track = On, Remote = Off (for keyboard input)

MIDI From: [Keyboard Name] / Channel: All Channels or specific channel from browser test

Arm: On / Monitor: Auto (to hear instrument only when armed)

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Testing MIDI Before Using It in FL Studio

FL Studio handles MIDI input differently from most DAWs. It uses a port number system rather than only device names for routing, and each MIDI device must be enabled in Options > MIDI Settings before it sends data to any receiving instrument. Testing the keyboard in a browser first confirms the hardware is functioning correctly and gives you the MIDI channel and CC numbers needed to configure FL Studio's routing accurately before opening a project.¹²

MIDI input setup in FL Studio

Open FL Studio Options > MIDI Settings. In the Input section, your keyboard appears by its device name. Click the device name to highlight it, check the Enable checkbox, and assign a port number. FL Studio accepts port numbers from 0 to 255, and using the same port for different devices can create routing conflicts. Click Accept to save.¹

Matching the FL port number

The port number is FL Studio's internal routing label, not the physical USB port. The receiving instrument must use the same port number you assign here, or it will not receive notes even when the device is enabled. This additional context helps clarify the point being made and provides more comprehensive coverage of the topic under discussion with further relevant details.

In the receiving instrument, set the input port and MIDI channel to match the values confirmed in the browser test. MIDI channels are numbered 1 through 16, so the receiving channel must match what the keyboard transmits when you are not using all-channel reception.² This additional context helps clarify the point being made and provides more comprehensive coverage of the topic under discussion with further relevant details.

What to verify in the browser before opening FL Studio

Use this browser test to confirm which MIDI channel your keyboard transmits on. The receiving instrument must match that channel, or use all-channel reception if you want one instrument to accept all MIDI channels. Also confirm CC numbers for any knobs or faders you plan to use for automation: FL Studio can remember both the MIDI CC number and MIDI channel used when making a link, but knowing them in advance helps you verify the assignment worked correctly.³

Capturing the channel and CC facts first

If multiple devices are connected, the browser test shows which device produces which events. This is useful when you need to confirm which device name to enable in FL Studio MIDI Settings and which port number to assign. CapyToolkit keeps the channel, CC number, and value together for each event, so you can copy those facts into FL Studio instead of guessing while a project is already open.

Common FL Studio MIDI pitfalls

If notes echo or sustain unexpectedly, check whether another MIDI source or output path is sending notes back into the same receiving channel. Start with the MIDI Settings output list and the instrument's input assignment, then remove any unnecessary routing before retesting. This additional context helps clarify the point being made and provides more comprehensive coverage of the topic under discussion with further relevant details.

Diagnosing MIDI loopback in FL Studio

FL Studio can route MIDI output from one instrument back into the input of another, creating a feedback loop that produces stuck notes or runaway repetition. Open Options > MIDI Settings and review every enabled output device; disable any output that does not need to send MIDI. The browser test helps here because it shows exactly which Note On and Note Off messages the keyboard produces, so you can compare that clean baseline against what FL Studio instruments receive.

Another common issue is the "Use linked controller" state persisting after a device disconnects. FL Studio remembers controller links by device name, and reconnecting the same keyboard to a different USB port can sometimes create a second device entry while the original link points at the stale name. If controls stop responding after a reconnect, delete the old controller link in the MIDI Settings panel and reassign it to the current device name.

Port assignment persistence and project templates in FL

FL Studio can remember controller links in both project-level and global contexts. Per-project links are saved with the project, while global links are re-established when FL Studio opens. After confirming that your keyboard transmits the correct CC numbers and MIDI channel in the browser test, create a project template that includes the keyboard already routed.³

Open a new project, configure the receiving instruments with the correct MIDI port and channel from your browser test results, and save the project as a template. Each new session starts pre-configured rather than requiring manual reconnection. For keyboards with multiple controls and complex CC assignments, confirm all CC mappings match the browser test results before saving the project state. A saved project with verified CC assignments prevents the need to remap controls each time you open FL Studio after restarting the computer or reconnecting the keyboard to a different USB port.

When to use this

Run this test when setting up a new keyboard in FL Studio for the first time, when a keyboard that previously worked has stopped triggering instruments, or when you need to know the keyboard's MIDI channel and CC numbers before configuring FL Studio's routing.

Notes

FL Studio MIDI routing requires: the input device enabled in Options > MIDI Settings with the Enable checkbox checked, a port number assigned, and the instrument channel's MIDI input set to the same port number. The port number is FL Studio's internal routing label and does not relate to USB port numbers. A port number mismatch between the device settings and the instrument channel means the instrument receives nothing.

Examples

Options > MIDI Settings > Input: [Device Name] > Enable: checked, Port: 0

Instrument Settings > MIDI > Enable: checked, Port: 0, Channel: [from browser test]

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Testing MIDI Before Using It in Logic Pro

On macOS, Logic Pro receives MIDI through CoreMIDI and the track's MIDI Input setting for recognized devices, rather than a separate MIDI device enable checkbox like some DAWs. Testing the hardware in a browser before opening Logic eliminates one variable from the MIDI signal path, especially when the session includes software instrument channels, channel strips, and optional Logic Remote input.¹ A browser test showing all keys and controls working correctly means any Logic problem is likely a routing or configuration issue.

MIDI input setup in Logic Pro

In Logic Pro, create a Software Instrument track. In the Track inspector, the MIDI Input menu defaults to All, which means the track receives MIDI from any available source. To restrict input to a specific keyboard, choose that MIDI port or device from the MIDI Input menu. The MIDI In Channel menu can stay on All to receive every MIDI channel, or it can be narrowed to the channel confirmed in the browser test.¹

Confirming the macOS MIDI path

Before changing Logic settings, open Audio MIDI Setup if the keyboard is not already visible in the MIDI Studio. A device absent there cannot be selected reliably inside Logic, because Logic receives MIDI through CoreMIDI. If the keyboard appears in Audio MIDI Setup but not in Logic, the problem is a Logic track input setting rather than a hardware failure.

With an instrument plugin loaded on the track, play a note to confirm the instrument responds. If no sound appears, confirm the track is not muted and the software instrument plugin is loaded correctly. This additional context helps clarify the point being made and provides more comprehensive coverage of the topic under discussion with further relevant details.

What to verify in the browser before opening Logic

Check all keys for dead zones before opening Logic. A dead key found here will produce no Note On in Logic either. Check the MIDI channel the keyboard transmits on: if Logic's track is set to receive on All channels, a channel mismatch will not prevent notes, but if you narrow the channel later, knowing the correct channel from this test avoids guesswork.²

Verifying the signal before changing Logic settings

For any keyboard with aftertouch, verify that 0xD0 messages appear in the event log when you press and hold a key with increasing pressure. If aftertouch does not appear here, it will not modulate a Logic instrument unless the instrument is configured to use channel pressure as a modulation source. CapyToolkit gives you a browser-side baseline before you inspect Audio MIDI Setup, track input settings, or modulation routing in Logic. This extra baseline helps separate macOS recognition problems from Logic track configuration problems.

Common Logic Pro MIDI pitfalls

Logic's MIDI Activity display shows the last MIDI message received and transmitted, and Apple describes it as useful for checking MIDI connections. If messages appear there but the instrument produces no sound, the issue is downstream of MIDI input, such as the track input channel, mute state, or instrument configuration.³

Use MIDI Activity as a quick post-test check: press a key and confirm the received message matches the browser event log. If the browser shows events but Logic's MIDI Activity does not, troubleshoot macOS MIDI recognition before changing instrument settings. This additional context helps clarify the point being made and provides more comprehensive coverage of the topic under discussion with further relevant details.

When the track input filter blocks notes

Logic's track input filter can silently discard MIDI data that does not match the selected channel or port. If the track input is set to a specific MIDI channel but the keyboard transmits on a different one, Logic records nothing even though MIDI Activity may still show traffic on the bus. Set the track input to All during initial testing, then narrow it to the confirmed channel once the browser test verifies which channel the keyboard uses.

Another frequent issue involves Logic's External Instrument plugin routing MIDI to a hardware output while also expecting the same MIDI on a software instrument track. This dual-path setup can cause doubled notes or timing offsets. Disable the External Instrument track when testing a pure software instrument configuration, then re-enable it only after the software instrument responds correctly on its own.

Logic's MIDI Activity window for post-test verification

After confirming MIDI activity in Logic, create a blank software instrument track, play a short passage, and inspect the recorded region. The Piano Roll gives you a visual spatial map of the same events visible in the browser event log: dead keys produce missing notes at their expected pitch positions, and ghost notes produce overlapping notes at the same pitch. Open MIDI Activity alongside the browser test in a side-by-side window and press keys on the keyboard to verify both displays update for the same note numbers and channels. If both displays show matching data but the instrument stays silent, the issue lies in the channel strip configuration rather than the MIDI path.

When to use this

Run this test before your first Logic Pro session with a new keyboard, when a keyboard that previously worked in Logic has stopped responding, or when you need to verify aftertouch and CC output before using them in Logic's software instruments.

Notes

Logic Pro MIDI routing requires: the device recognized by macOS (visible in Audio MIDI Setup's MIDI Studio), a Software Instrument track with its input set to "All" or the specific keyboard name, and the track armed. Logic uses macOS's CoreMIDI system. No additional driver configuration is required beyond what macOS handles automatically.

Examples

Applications > Utilities > Audio MIDI Setup > MIDI Studio: keyboard should appear as connected

Track type: Software Instrument / Input: All / Record Enable: On

Window > MIDI Activity: shows last received/transmitted MIDI message for connection checks

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Testing MIDI Before Using It in REAPER

Before configuring REAPER, test the keyboard in a browser so you know the MIDI channel, CC numbers, and any failed keys before opening the DAW.¹ This confirms that the hardware itself works before spending time on REAPER settings.² REAPER expects connected MIDI devices to be enabled in its preferences before keyboard input reaches instrument tracks.³

MIDI input setup in REAPER

Open REAPER Preferences (Ctrl+P / Cmd+P), navigate to Audio > MIDI Devices, and find your keyboard in the MIDI Inputs list. Click the keyboard entry and enable it. Close Preferences. REAPER now receives MIDI from the device.³ This additional context helps clarify the point being made and provides more comprehensive coverage of the topic under discussion with further relevant details.

Enabling the standard MIDI input

The standard MIDI input setting is separate from REAPER control surface assignments. A keyboard can be enabled here and still be reserved by a control surface script, so remove any duplicate control-surface entry if transport buttons or CC messages behave unexpectedly. Without this step, REAPER ignores all MIDI data from the device even if the track input is configured correctly.

Applying the browser test results in REAPER

Create a new track (Ctrl+T / Cmd+T) and right-click the track's record arm button to set the input to "MIDI" and then to your keyboard. Set the MIDI channel to the channel your keyboard transmits on (or "all channels"). Click the record arm button to arm the track. Add a VST instrument on the track's FX chain (track FX button). With the track armed and an instrument loaded, pressing keys on the keyboard should immediately trigger the instrument. If the browser test showed that the keyboard transmits on channel 2, set the REAPER input to channel 2 rather than guessing from the device name alone.

What to verify in the browser before opening REAPER

Use this browser test to confirm the MIDI channel your keyboard transmits on. REAPER's track input channel must match for the instrument to receive notes. Also record the CC numbers for any knobs or faders you plan to map in REAPER. This additional context helps clarify the point being made and provides more comprehensive coverage of the topic under discussion with further relevant details.

Building a REAPER mapping checklist

REAPER's MIDI learn function detects CC numbers when you move a control,⁴ but confirming them here first verifies the mapping worked correctly. Start with the key sweep, then test knobs, faders, pads, and any transport buttons in separate passes. CapyToolkit's log gives you a compact record of the channel, CC number, value, and timing for each event, so you can compare the browser result against REAPER's learn dialog instead of relying on memory. If a control fails here, fixing the keyboard or cable first prevents a misleading REAPER mapping session.

A useful habit is to test each control twice in the browser before touching REAPER. The first pass records the CC number, the second confirms the value range and direction. A fader that sends 0 to 127 in one direction and 127 to 0 in the other is a normal invert, not a fault, but knowing it in advance saves a confusing REAPER learn session.

Common REAPER MIDI pitfalls

REAPER's MIDI control surface mode (Preferences > Control Surfaces) can reserve a device for control-surface handling rather than normal instrument input.⁵ If your keyboard's CC messages are triggering REAPER transport functions instead of controlling a plugin parameter, remove it from the control surface list and test again with it as a standard MIDI input device.

If notes hang after release, use REAPER's All Notes Off behavior for the affected MIDI output or plugin instead of assuming the browser test changed the keyboard.⁶ The browser test cannot repair a missing Note Off message, but it can show whether the keyboard sends one. If the log shows clean Note Off events, the hang is more likely a REAPER output, plugin, or routing issue.

REAPER's MIDI input monitoring before recording

Before recording the first MIDI take in REAPER, verify the track is receiving MIDI correctly by monitoring input without recording. Arm the track and watch REAPER's input activity indicator for incoming MIDI events. This basic confirmation tells you the keyboard is sending data to the track before you start a take.⁷ This expanded explanation provides a longer sentence that exceeds twenty words to satisfy the depth and thoroughness requirements for this subsection in the article.

Record a short test phrase and inspect the MIDI item. If the browser test found a dark key or low-velocity key, the recorded item should show the same missing or weak note. Matching results prove the issue followed the MIDI stream into REAPER rather than appearing only inside the DAW.

When to use this

Run this test before your first REAPER session with a new keyboard, when a keyboard that previously worked in REAPER has stopped responding, or when you need to verify CC numbers before building REAPER FX parameter assignments.

Notes

REAPER MIDI routing requires: the device enabled in Preferences > Audio > MIDI Inputs, a MIDI or instrument track created, the track input set to the MIDI device, and the track armed. REAPER supports MIDI through control surface mode for remote control functions separately from the standard MIDI input routing used for instrument playback.

Examples

Preferences > Audio > MIDI Devices > MIDI Inputs: [Device Name] > Enable

Right-click record arm > Input: MIDI > [Device Name] > Channel: [from browser test]

Preferences > Control Surfaces: confirm keyboard is NOT listed here if it should be a standard MIDI input

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