Final answer:
The dwarves likely used instruments like the banjo, fiddle, and mandolin to accompany their songs, chosen for their portability and volume in communal environments.
Step-by-step explanation:
The dwarves accompanying their songs would have used instruments that were both practical for travel and conducive to their environment. In most folk music traditions, lightweight and homemade instruments were preferred due to the ease of transportation and the ability to craft them from locally available materials.
Considering this, three instruments the dwarves might have used include the banjo, which features a resonator to amplify its sound, the fiddle (another name for the violin) known for its shrill and piercing tone capable of carrying over distance, and the mandolin, played rhythmically and percussively to increase its volume.
These choices reflect the adaptability of musicians who required their music to be heard over large gatherings or in outdoor settings.