Add custom content to cart and checkout pages (only if a certain category is in the cart) with an action hook

conditional cart checkout hook by catetory

// CHECK FOR SPECIFIC PRODUCT CATEGORY IN CART
function madcow_custom_category_is_in_the_cart($categories) {
    // Products currently in the cart
    $cart_ids = array();
    // Categories currently in the cart
    $cart_categories = array();
    // Find each product in the cart and add it to the $cart_ids array
    foreach (WC()->cart->get_cart() as $cart_item_key => $values) {
        $cart_product = $values['data'];
        $cart_ids[]   = $cart_product->id;
    }
    // Connect the products in the cart w/ their categories
    foreach ($cart_ids as $id) {
        $products_categories = get_the_terms($id, 'product_cat');
        // Loop through each product category and add it to our $cart_categories array
        foreach ($products_categories as $products_category) {
            $cart_categories[] = $products_category->slug;
        }
    }
    // If one of the special categories are in the cart, return true.
    if (!empty(array_intersect($categories, $cart_categories))) {
        return true;
    } else {
        return false;
    }
}

// ADD BANNER TO CART PAGE IF A SPECIFIC CATEGORY IS IN THE CART
add_action('woocommerce_before_cart', 'madcow_above_cart_and_checkout_message');
add_action('woocommerce_after_order_notes', 'madcow_above_cart_and_checkout_message');
function madcow_above_cart_and_checkout_message() {
    $categories = array('music');
    if (madcow_custom_category_is_in_the_cart($categories)) :
        echo '<div class="top-cart-message"><h2>This is our cool message</h2></div>';
    endif;
}