Get posts from another category with same tag as current post?

This is a bit complicated to explain so bear with me…

Q: Inside the loop of a category template, how can I spit out a list of other posts from another category which share the same tag as the current post?

Eg. On my ‘Bands’ overview page, I have a list of bands (each one of which is a post in the ‘Bands’ category), and beside each band I want to show the latest 3 releases (a post from the ‘Releases category) and the first image from each post. Each band and release post is tagged with a band name.

$artist is the tag slug but I don’t think it’s working inside the get_posts query….

Thanks for reading 🙂

Inside the loop of a category template:

<?php
$posttags = get_the_tags();
if ($posttags) {
	foreach($posttags as $tag) {
		$artist = $tag->slug . ' ';
	}
}
?>

<!-- Latest releases -->
<div class="span-4 last">
	<h3>~ Latest Releases</h3><?php /* just to test that we have the artist slug... */ echo $artist; ?>
	<ul>
	<?php
		$rand_posts = get_posts('numberposts=1&tag=$artist&category=releases');
		foreach( $rand_posts as $post ) :
		?>
		<li><a href="<?php the_permalink(); ?>"><?php the_title(); ?></a></li>
		<?php endforeach; ?>
		</ul>
</div>