plonky

adjective3

1. •
   (informal) Chiefly of pianos: having an unappealing, thudding sound.

   • They both possess a light, slightly nasal voice, but whereas Siffre has his excellent guitar work to back up his vocals, O'Sullivan only has that same old plonky piano and his arranger. — 1973
2. •
   (figurative) Dull, stiff, unadventurous.
3. •
   (slang) Of wine: having the qualities of plonk; cheap and inferior.