Download Heartopia MIDI Player

This is an unsigned app from an indie developer

Because it isn't code-signed, Windows and antivirus software may show warnings — that's normal. If you're willing to trust this file, follow the steps below to allow it. If you don't trust it, please don't download or use it.

① Antivirus may flag it

Auto-play tools like this simulate keyboard input, so antivirus software sometimes plays it safe and treats it as suspicious — or even moves it to quarantine. It is not a virus; it is a false positive. If the app disappears after downloading, or gets blocked the moment you run it, here is what to do: first, restore it from your antivirus quarantine and choose to trust or allow it. If you trust the app and do not want it blocked again, open Windows Security → Virus & threat protection → Manage settings → Exclusions and add the whole folder you extracted; it will not be scanned after that.

② If a blue warning appears when you run it

When "Windows protected your PC" appears, click "More info", then click "Run anyway".

③ Allowed it but it still won't open?

On a few machines it still fails with a Python runtime error even after you allow it. That is usually Windows marking the downloaded files as blocked. Two steps to clear it.

Open PowerShell first: press Windows + R to bring up the Run box, type powershell, and click OK. Searching the Start menu for PowerShell works too.

Then replace the double-quoted path below with your extracted folder, paste the whole line, press Enter, and open the app again. The example assumes Downloads and a Windows username of duduru:

To get the path: Shift + right-click the folder and choose "Copy as path". What you get already includes the quotes, so it can replace the whole quoted part.