Caution
IMPORTANT DISCLAIMER Howl is a free hobbyist app that carries no warranty, and we accept no liability. Any use of the app and any use of electronic stimulation ("estim") devices is at your own risk.
Howl is an Android app that controls and generates patterns for estim devices, for erotic adult entertainment.
Its features include: -
- Playback of funscript files, using an original positional algorithm.
- Playback of HWL files, Howl's native format, often used for preconverted audio files.
- Built-in "activities". These are patterns with random elements that Howl generates in real-time.
- A wave generator with various different parameters and shapes.
- Automatic synchronisation of funscript files with videos, using our "Howl Sync" add-on for Kodi.
- Ability to record anything that Howl can play to an HWL file, enabling the easy creation of custom patterns.
A pre-built APK file for the latest version can be found here. You simply need to install the APK file on your Android device.
Additional downloads, including older versions and the Kodi add-on, may be found on the main Releases page.
The output devices currently supported by Howl are: -
- DG Lab Coyote 3. This is the device Howl was originally developed for, and generally works well.
- DG Lab Coyote 2. The main downside of the older Coyote 2 is that it is only capable of updating 10 times per second, as opposed to 40 on the C3. Some of Howl's faster patterns might change too quickly to be well represented (if needed you can use the "playback speed" global setting to slow anything down).
- Almost any device that accepts audio input (more experimental, see notes in wiki)
The Howl app is intended to run on any version of Android from 8.0 (released in 2017) onwards. However testing with very early versions has been limited.
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Howl expects you to set up your electrodes such that channel A creates a "lower down" sensation, and channel B creates a "higher up" one. This is especially important when playing funscripts, as our algorithm will distribute power according to the positions in the funscript, so that you feel sensations in the right place.
Always follow best practice and your device manufacturer's instructions, and do not under any circumstances connect any electrode above your waist.
The wiki provides further details, including information on calibrating frequencies optimally for your setup for Coyote 3 owners.
Howl's main controls are displayed in the top section of the screen.
The plus and minus buttons adjust the overall power on their corresponding channel up and down. The full range is 0 to 200. The maximum level you can turn the power up to is also governed by the power limit configured on the settings page (70 by default).
The step size for the power controls defaults to 1, but this can be increased on the settings page if you would like larger steps. A long press on the minus control allows power on the corresponding channel to be quickly set to zero.
Gives a quick visual indication on what is being output on channel A (left meter) and channel B (right meter). The height of the coloured bar shows the amplitude (pattern power). The colour of the bar gives a guide to the frequency between red (lowest frequency) and yellow (highest frequency).
Toggles the mute function. When muted, Howl will not send any output to your device. This is useful if you need a short break, for example to adjust your electrodes.
Player time still advances when mute is on, allowing funscripts to remain in sync.
Toggles a function that automatically increases the power periodically. The time delay between increases is configurable on the "Settings" page, and can optionally be different for each channel.
To help with safety and predictability, the auto increase will only happen when the following conditions are met: -
- The auto increase toggle button is on.
- Something is actively being played.
- Mute is off.
- Power on the channel is higher than zero (you must manually set the power to at least 1 before automatic increases will start).
The power level increases by 1 each time the configured delay elapses - this function does not use the configured power step size. This is by design and allows for the smoothest possible increase over time.
Toggles the display of pulse charts, which give a visual representation of what output Howl generated recently.
The button toggles between 3 chart modes: -
Off (default) No chart is displayed, and there is no performance overhead.
Combined A single chart is displayed, with time on the X axis (most recent on the right) and power on the Y axis. The top of the chart corresponds to maximum output power, and the bottom of the chart to zero power. The colour of each point denotes the channel and gives a rough guide to the frequency. Channel A points go between red (lowest frequency) and yellow (highest frequency). Channel B points go between blue (lowest frequency) and green (highest frequency).
Split Two separate charts are displayed. For both charts the X axis is time (most recent on the right), red points are on channel A, and blue points are on channel B. The chart on the left shows power (maximum at the top and minimum at the bottom). The chart on the right shows frequency (maximum at the top and minimum at the bottom). The split chart can be harder to understand, but is useful if you need a more accurate display of exactly what the frequency is doing.
The charts record the last 5 seconds of data. The charts and meters always show 40 pulses per second, regardless of the actual pulse rate of the output device.
Toggles the channel swap feature. When active, the output on channel A and channel B is swapped. This is helpful if you connected your electrodes the wrong way round, or if you are playing a converted audio file that had different electrode placement to Howl's preferred setup.
It does not swap the power controls, only what is output (i.e. channel A power always controls Coyote channel A regardless of this setting). Special effects options always apply to the channel they are labelled with, and do not swap.
This slider sets the minimum and maximum frequency that Howl can use during playback. The full range of frequencies between these values may be used for output. Everything Howl plays is mapped in real-time to the range you've set. So you can always adjust this control to your liking, whatever content happens to be playing.
The "Player" tab contains Howl's central functionality, the media player and pulse recorder. Everything in Howl plays via the player, including features in other tabs like the generator and activities. So settings that the player offers like changing playback speed, or applying special effects, can be applied to anything that Howl can play.
The open button (folder icon) allows you to play back files that are stored locally on your device. HWL files and funscript files are currently supported. Your files need to be stored somewhere on your device that doesn't require any special permissions to access (I generally just use a subfolder inside "Documents").
Playback speed This controls the rate at which the player counts time, allowing any content Howl can play to be sped up or slowed down. The playback speed can be set from 0.25x to 4.0x, in increments of 0.25. For example setting this control to 0.5 will play at half speed. Setting it to 2.0 will play at double speed. 1.0 is the standard setting and plays at normal rate.
Remote latency (seconds) This setting configures the expected latency between Howl and the "Howl Sync" Kodi add-on when funscripts or HWL files are loaded using Howl's remote API. The player will correct for this latency, so adjusting this control to an appropriate value should allow near perfect sync to be obtained. This setting is for remotely loaded files only, and has no effect on files you load locally from your Android device.
Show sync fine tune When enabled, a control will appear below the player allowing slight adjustments to Howl's playback position (up to +/- 0.5 seconds). This can be helpful if you are trying to sync up a file you played manually with other content (for example a video). The sync adjustment is a temporary control and will reset to zero upon opening a new file. For correcting typical latency when using the Kodi add-on, use the persistent "Remote latency" setting instead.
The player settings page also contains the advanced settings for funscripts, which are explained on the funscript wiki page.
Advanced users who want to further tweak Howl's output can apply various interesting special effects (accessed via the "magic wand" button). These work with all types of content, and can sometimes very significantly change the output.
See the special effects wiki page for descriptions of all the available effects and their functions.
Howl's pulse recorder is situated at the bottom of the "Player" tab, below the media player control. It is capable of recording output from anything Howl can play, and saving it as an HWL file for later use. This makes it easy to create your own custom patterns by combining any existing content.
The recorder has two different modes: -
Passive (switched off) The last 2 minutes of output are continuously recorded to a circular buffer. This means that if you're playing one of Howl's random activities and happen to get a pattern you really like, it isn't gone forever once the pattern changes. You can simply head over to the recorder and save the recent output, allowing you to play it again later, or make your favourite part into a loop.
Active (switched on) Allows you to create your own custom recording (up to 2 hours). You can record anything that Howl can play, for example generator patterns, or parts of other HWL files. This allows you to combine different content into a custom pattern that's perfect for you.
When in active mode a dedicated toggle button turns recording on and off. This allows you to "punch in" and "punch out" at the right points when playing back a file, in order to capture the part you want. You can also just leave it toggled on if you want to record everything the player plays.
It's best to leave the recorder in passive mode when you are not using it. When in active mode, Howl uses a special playback mode that is pulse accurate rather than time accurate. This allows the recording of content like existing HWL files without quality loss. But this mode is worse for general playback, since funscripts will no longer stay in sync with videos, and all timing effects such as latency compensation are disabled.
The "Generator" feature generates continuous waves in real-time, with a wide range of parameters. The shapes, speeds and frequencies of the waves can all vary, so a vast number of different combinations is possible.
You'll probably find some patterns that are highly pleasurable, and some that aren't great. Every time you press the "Random" button, you'll get different waves with a new set of parameters. Keep trying your luck, and you're almost guaranteed to find something you enjoy.
You can tap on the "Channel A" or "Channel B" parameter box if you'd like to manually configure the wave parameters yourself.
There's an "Automatically change parameters" option which is designed to be a provide a more continuous experience by changing the wave parameters over time. The concept is that it's a bit like somebody else playing around with the knobs and buttons on a control box for you. It's capable of adjusting parameters like speed, power and frequency smoothly over time at different rates. So the experience should evolve over time, in contrast to the random button which just immediately rerolls everything.
The probability of speed, power, frequency and shape changes can all be set independently when using the automatic mode. The maximum value of 1.0 here corresponds to an average of 10 changes per minute. So 0.1 would be 1 change per minute on average etc. But keep in mind these are just probabilities rather than guarantees, depending on chance you may see significantly more or less changes than the average.
Howl offers a number of built-in "activities". These are patterns with random elements that Howl generates in real-time. They provide a more interesting alternative to just having fixed preset patterns.
The list of activities wiki page gives information about all of the available activities. This includes what they represent, what their settings do (where applicable) and any extra details about how they work.
The manual feature allows you to control your estim device directly. It uses a dual touchpad system, which is reminiscent of video game controls.
- The left pad controls channel A, the right pad controls channel B.
- The center of the circle represents zero power, rising to maximum power at the edges.
- The direction of movement from the center determines the frequency. The highest frequency is at the top of the circle, the lowest frequency is at the bottom.
The circle is mirrored vertically around the center. For example moving directly left or directly right does the same thing. This gives multiple positional choices to improve ergonomics, and makes swiping through the center easier.
Touchpad center rate Controls how quickly the touchpads return to the center when you stop touching them. Higher values return to the center more quickly. You can set this to zero to disable automatic centering and keep the pads in the last touched position.
Smoothing Controls how much smoothing is applied to your touch input. Lower values are more responsive, higher values will move towards the touched position more gradually over time. Higher smoothing values can work well with the center rate set to zero, since then you can just tap a position in the circle and the output will smoothly shift towards it (allowing for easier one handed operation).
Selects what kind of output device Howl is using. When connecting a Bluetooth device the appropriate output type will be selected automatically.
Supported output types are: -
- Coyote 3
- Coyote 2
- Audio (continuous) - continuous output for audio devices, see wiki for details.
- Audio (wavelet) - wavelet output for audio devices, see wiki for details.
These additional parameters, which are implemented by the Coyote hardware, are available when using a Coyote 3. Functionality should be exactly the same as the equivalent settings in the DG Labs app.
Channel A/B Frequency Balance This controls the relative strength of high and low frequencies on that channel. Higher values give stronger low frequencies. Howl's default is 200. Some guidance on optimising this for your own electrode setup is available in the wiki.
Channel A/B Intensity Balance This seems to be another way to adjust the very lowest supported frequencies. E.g. when it would normally play 1Hz, the hardware might play 10Hz instead if you increase the intensity balance a bit. I don't find this useful, and always leave it set to 0.
All of the power options can be configured independently for each channel, which is helpful when using different types of electrode.
Channel A/B Power Limit Limits output device power on that channel to the selected level. The maximum output power level is 200.
Power control step size This sets how much the power level changes by when you press the large plus/minus buttons in Howl to change the channel A or B power. The default is 1. This is a convenience setting for users who like to use high power levels, allowing them to be reached without having to press the adjustment buttons as many times.
Power auto increase delay This sets how long the auto power increase feature will wait between power level increases. See the section on the auto increase power button (under "Main controls") for further details.
Allow remote access This setting enables Howl's remote access API, allowing it to be controlled by other apps, such as the Howl Sync Kodi add-on. Remote access is disabled by default.
Remote access key This sets the key that other apps must submit (using HTTP bearer authentication) in order to use Howl's remote access API. This acts as a basic security measure. Use of the API on unsecured networks is not recommended, since the key is sent in plain text, so an attacker could easily obtain it. The key is set to a random 12 character string by default.
Show animated power meters This setting causes animated pulse meters to be shown for each channel on the main control panel. Disabling it may help users who find animations distracting, and also reduces Howl's battery usage (as display refreshes by the meters or charts are a large factor in that).
Show debug log tab When this setting is enabled, a "Debug" tab becomes visible, located to the right of "Settings" on the main tab bar (on narrower devices you may need to scroll the bar to see it). The debug tab shows information from Howl's internal log, which may sometimes be useful for troubleshooting issues.
The Howl Sync add-on for Kodi allows .funscript files for videos that you're playing in Kodi to be automatically sent to Howl and synchronised with the video position. It is by far the most convenient method for playing funscripts. See the wiki for installation and setup details.
Can I use Howl on iOS? No. Howl is a native Android app, so it's unlikely that an iOS version will ever exist (that would require rewriting most of the app).
Howl is a simple hobbyist app, and does not include any adverts or tracking. It does not send anything over the internet, and doesn't require internet access.
On Android versions before 12, the app will ask for location permissions. Howl does not track your location at all, and this is simply because the location permission is required to scan for Bluetooth devices on those versions. On later versions of Android, the app only requires Bluetooth permissions.
All original code is released under the MIT License. There is an additional stipulation that if you distribute this app or any part of it (with or without changes), you may not use the name Howl, or any very similar name. This is to help make it clear to users that your distribution is not associated with this project.