$item.list_rank
Using Jamroom
Here's a different version. Doug pointed out that since there is only 1 in the list it will always be position #1, so in this version we get the top 50. If the current song is in the top 50 then its positon in that top 50 is shown.
{capture assign="list_tpl"}
{literal}
{foreach $_items as $item}
{if $item._item_id == $_params.my_id}
my place in the top 50 list is: {$item.list_rank}
{/if}
{/foreach}
{/literal}
{/capture}
{jrCore_list module="jrSoundCloud" chart_field="soundcloud_stream_count" chart_days="365" limit=50 template=$list_tpl my_id=$item._item_id}
This one is for soundcloud songs, adjust the variables as you need them.