I am currently composing something and I really want to have this sound in my piece. It sounds like a small hammer hammering on metal.
It starts at 1:08:07 (Verwandlungsmusik, Rheingold)
What is this and is it an instrument at all?
Wagner actually specified in the score for 18 anvils to perform this section. Since the scene is moving down to Nibelheim (and later back up from Nibelheim) where the Nibelungs are hard at work smithing the titular gold, Wagner wanted to represent this sound as accurately as possible.
If you're looking for the specific instruments used in this specific recording, I'm not sure I can help. But the intent was for these to be 18 anvils.
For another rendition, here is the famous Solti recording with Vienna.
It sounds like a small hammer hammering on metal.
Good ear; while Wagner originally called for anvils, modern productions use metal hammers on heavy pieces of scrap metal to create this effect. Here's the Victoria Symphony, using I-beams and manhole covers, and the Halle Symphony using steel plates and I-beams. I once played with a group that used brake drums for the same effect; you can hear the recording here.
One good substitute for an anvil that I have found is the "double-shoulder railroad tie plate":
If you're a little resourceful, you can find these discarded by the hundreds near old rail lines. Clean up the rust and paint it if you like.
Put it on a firm support resting on the shoulders (i.e., upside-down). You can control the amount of "ring" by striking it directly above the shoulders, or farther away. A small ball-peen hammer makes a good striker.
Yes, the piece is scored for anvils. It's the Nibelungs forging their gold. In the Met's documentary, "Wagner's Dream" there is a shot of the orchestra playing the anvils. As part of their production of The Ring, the Met offered this section as a downloadable ringtone. Hummm. Perhaps it was the original Ring-tone? Tom Hayes