You have to take into the account that all tunes tend to become less important as time goes by. Most of the 10,000 sales / day are divided mostly between the items that have best search visibility throughout the genres. So at any point in time, only a certain amount of your portfolio is “alive”. But the scale is still relevant. If your portfolio is only 20 tunes, only say 10 of them are alive but if your portfolio is 200 tunes, 100 of them might be. The only question that matters is - how probable it is that the customer finds your tune. The smaller the portfolio, the smaller the chance.