This is the 14423rd most frequent German word.
klangvollen
"Resonant" or "full of sound."
Here, 'klangvolle' describes the noun 'Stimme' (voice) as tuneful and rich in sound attributes.
Die Sängerin hat eine klangvolle Stimme.
The singer has a tuneful voice.
In this sentence, 'klangvolle' characterizes the noun 'Echo' (echo) as possessing a pleasant, harmonic quality.
Ich liebe das klangvolle Echo in den Bergen.
I love the melodious echo in the mountains.
Here, 'klangvollen' describes 'Töne' (tones), expressing the aesthetic sound quality conveyed by the piano.