You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: listen_hrtf_frontback.m
    path of file: ./repos/HRTF-Individualization/model/matlabcode/functions/gui/play
    
    the code of the file until where you have to start completion: function [ sound_out ] = listen_hrtf_frontback(hObject, eventdata, handles)
% Listen to HRTFs in Azimuth 0 and 180 with Elevation 0

global current_db
global DB
global current_subject
global fs
global ANGLES

set(handles.status_text,'BackGroundColor', 'r'); 
set(handles.status_text,'ForeGroundColor', 'w'); 

    if (strcmp(current_db,'universal') == 1)

    [~,hrir_length,fs] = get_matrixvalue_universal(0,0,current_subject);
    azimuth_values = [0 180];

    % Play HRTFs in Loop
    for i = 1:length(azimuth_values)
        value = get_matrixvalue_universal(0,azimuth_values(i),ANGLES);    
        out_left = squeeze(DB(current_subject,value,1,1:hrir_length));
        out_right = squeeze(DB(current_subject,value,2,1:hrir_length));  

    
function [ sound_out ] = listen_hrtf_frontback(hObject, eventdata, handles)
% Listen to HRTFs in Azimuth 0 and 180 with Elevation 0

global current_db
global DB
global current_subject
global fs
global ANGLES

set(handles.status_text,'BackGroundColor', 'r'); 
set(handles.status_text,'ForeGroundColor', 'w'); 

    if (strcmp(current_db,'universal') == 1)

    [~,hrir_length,fs] = get_matrixvalue_universal(0,0,current_subject);
    azimuth_values = [0 180];

    % Play HRTFs in Loop
    for i = 1:length(azimuth_values)
        value = get_matrixvalue_universal(0,azimuth_values(i),ANGLES);    
        out_left = squeeze(DB(current_subject,value,1,1:hrir_length));
        out_right = squeeze(DB(current_subject,value,2,1:hrir_length));  

        play_sound([out_left'; out_right'],fs);
        pause(0.2)
    end