Midi Keyboard using sound recordings?

I am trying to implement a virtual pipe organ that is played in real-time using midi keyboards. When a note is pressed on a keyboard or clicked on the gui, a corresponding sound recording of the note should play on repeat, until the key is released. The start and end of each recording has been cut so that it can be looped seamlessly. I'm using MATLAB and Audio Toolbox. I've created the GUI using App Designer and it consists of state buttons for each key of the instrument.

Whether I use the deviceWriter or sound(y, Fs) functions, I can't get more than a single note to play without MATLAB freezing in what seems to be an infinite loop. I've tried:

• Using the ValueChanged callback and having the file play while a key button's value is 1
• Using regular buttons instead of statebuttons - clicking on these just plays the audio file for one iteration
• Editing the simplesynth example at https://uk.mathworks.com/help/audio/ug/midi-synthesizer.html to play my sound file instead of a frequency - Sound plays once then seems to be stuck in an infinite loop
• Using the playblocking function to play the sound - this doesn't cause the infinite loop but after each repeat of the sound file, there is a split-second pause where there is no sound

Is it possible to create a midi keyboard in matlab that plays sound files for each note, rather than just playing frequencies? If so, where am I going wrong? And if not, please could you point me in the right direction as to how I can implement a solution, perhaps using external plugins?