I've super easy question:

I've code:

<?php if (function_exists("insert_audio_player")) {insert_audio_player("[audio:|titles=]"} ?>

This code results audio player to my page in wordpress. I have to call custom area inside this code. My custom area code is:

<?php print_custom_field('tc_filename'); ?>

Something similar to:

<?php if (function_exists("insert_audio_player")) {insert_audio_player("[audio:<?php print_custom_field('tc_filename'); ?>|titles=<?php print_custom_field('tc_title'); ?>]"} ?>

How do i demand second code inside first? Thx.

Edit: As mentioned through the OP, the print_custom_field() function uses echo instead of return, which means this answer won't work with this specific situation. See @Jacob's answer for any better solution.

Do this:

<?php
    if (function_exists("insert_audio_player")) {
        insert_audio_player(
            "[audio:" . print_custom_field('tc_filename') .
            "|titles=" . print_custom_field('tc_title') . "]"
        );
    }
?>
<?php 
if (function_exists("insert_audio_player")) {
    insert_audio_player("[audio:".print_custom_field('tc_filename')."|titles=".print_custom_field('tc_title')."]"
} ?>

You may make this simpler to see using [cde]

sprintf()

Edit: according to your comment, paper_custom_area really echo's the area, and does not give it back, if there's no return function you should use, you should utilize Output Buffering.

Use a new function, which calls paper function but returns it rather than printing it towards the screen:

<?php 
if (function_exists("insert_audio_player")) {
    insert_audio_player(sprintf(
        '[audio:%s|titles=%s]', 
        print_custom_field('tc_filename'), 
        print_custom_field('tc_title')
    ));
} 
?>    

And employ

function get_custom_field($field) {
    ob_start();
    print_custom_field($field);
    return ob_get_clean();
}
<?php 
if (function_exists("insert_audio_player")) {
    insert_audio_player(sprintf(
        '[audio:%s|titles=%s]', 
        get_custom_field('tc_filename'), 
        get_custom_field('tc_title')
    ));
} 
?> 

then :

<?php if (function_exists("insert_audio_player")) {insert_audio_player("[audio:".function2()."|titles=".function3()."]"} ?>