"end of the sample audio file" << What is the length in seconds of this audio file?
And: What is the issue that you can't handle even though you set the length of 100 seconds?
.If your sample has a loop and includes an additional tail piece at the end of the loop section, in Polyphone you can use the tail-loop symbol found in the loop cell(s) in the instrument section. After you take your finger off the button, the loop plays until it ends, and then the tail (end) part that follows the loop is played.
Asking your synthesizer to play a sound indefinitely means that playback is no longer under your control. Because you should be able to terminate that sound in a legal way using that device.
There are normally two ways to do this: a) stop pressing the keyboard key and b) stop pressing the damper pedal. // special case: Or maybe there is a specially designed "Hold" button in the keyboard. It may be necessary to make it turn off by pressing it again.
If, in any of these situations, the playback sound doesn't fade out or doesn't stop (cut) after a certain amount of time, we have a problem.
It may also be a (non-technical) solution to squeeze one side of a clothespin that you split into two parts, between the two keys of the Keyboard. But for this you need a separate dedicated (physical) keyboard part that plays this looped part.
For such things, DJ equipment may have specially designed apps. Because it looks more like FX work than normal music work.
