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diff --git a/HOWTO.md b/HOWTO.md
index d948e59..059a039 100644
--- a/HOWTO.md
+++ b/HOWTO.md
@@ -25,6 +25,8 @@ cmake --build build
 
 ## Testing
 
+**Commit Policy**: Always run tests before committing. Refer to `CONTRIBUTING.md` for details.
+
 To build and run the tests, you need to enable the `DEMO_BUILD_TESTS` option in CMake.
 
 Available test suites:
@@ -69,3 +71,30 @@ The executable will be located at `build/spectool`.
 ```bash
 ./build/spectool play path/to/input.spec
 ```
+
+### Spectrogram Viewer (`specview`)
+
+A command-line tool for visualizing spectrogram files in ASCII art.
+
+#### Building the Tool
+
+`specview` is built along with `spectool` when enabling `DEMO_BUILD_TOOLS`.
+
+```bash
+cmake -S . -B build -DDEMO_BUILD_TOOLS=ON
+cmake --build build
+```
+The executable will be located at `build/specview`.
+
+#### Usage
+
+**View a spectrogram file:**
+```bash
+./build/specview path/to/input.spec
+```
+
+## References and links
+
+drum-kit: https://drive.google.com/file/d/13tc7XjkMg-tigvje5qpp6XazK-VcOjoc/view
+(got from https://www.reddit.com/r/Drumkits/)
+