Death Mountain Howling Stone Location & Combination
The Howling Stone on Death Mountain can be accessed the very first time you're traveling through the area as a Wolf - if you miss it during this time then you'll have to come back much later in the game when you can transform to and from a Wolf any time you want with the Shadow Crystal.
As for the location of the Howling Stone itself, it's found almost at the peak of Death Mountain, the exact location is shown in the screen shot above. You'll actually have to run right past this stone when you're traveling up Death Mountain which makes it quite hard to miss.
The song combination for this stone is rather straight forward too, and is shown in my screen shot below. If you're having trouble seeing the pattern just click on my screen shot to enlarge it.