Chord of Calling is a rare Instant card from Ravnica Remastered (RVR), collector number 345. Current market price: $6.99 (foil $10.15), TCGplayer market prices via Scryfall.
Convoke (Your creatures can help cast this spell. Each creature you tap while casting this spell pays for {1} or one mana of that creature's color.) Search your library for a creature card with mana value X or less, put it onto the battlefield, then shuffle.