Camilo - I suspect that the problem is that the audio player p is a local variable in your function. So as soon as the last line of code in the function is executed, the function is finished and is removed from the function call stack and so all variables declared within are "destroyed" including p...and so playback will end before it begins. Since you are using GUIDE, you can get around this by saving the player to the handles structure so that it persists outside of this function:
function pushbutton1_Callback(hObject, eventdata, handles)
[a, fs]=audioread('909.wav')
handles.p=audioplayer(a,fs)
guidata(hObject, handles); % <------ important! saves the updated structure
play(handles.p)
Now p is part of handles (and you must call guidata to save this updated structure). Try this out and see what happens!
Alternatively, you can use playblocking instead of play as playblocking does not return control until playback completes.
