Hopefully some constructive comments -
There’s a couple of “unusual features” that you may not have noticed:
The “echo” setting is in seconds, but is marked in milliseconds.
There is no echo unless the echo volume is set greater than 100%.
It would probably be more accurate to describe the effect as “speed change” with “delay” as I presume that the effect is intended to change both tempo and pitch (rather than changing the pitch while maintaining the same tempo) and that the “echo” effect is intended to be a single delayed repeat (rather than a repeating or reverberating echo).
The only change required for the effect to work on Linux is changing the file extension to lower case, then it works exactly the same as on Windows.
Great demo MP3