Price$5.12 – $17.61
Buy on TCGplayerChord of Calling
Instant
LegalRank #535
Convoke (Your creatures can help cast this spell. Each creature you tap while casting this spell pays for 
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.
KeywordsConvoke
Why is this card good?
Chord of Calling is one of green's premier instant-speed tutors, and the convoke is what makes it sing. Tapping a board full of creatures (or tokens) lets you cast it for a fraction of its printed cost, often finding a key piece end-of-turn or mid-combat for "free."
The instant speed is the real selling point. You can wait until your opponents commit, then grab the perfect answer or combo piece — a sac outlet, a hatebear, a wincon — and put it straight onto the battlefield. That flexibility is huge in any toolbox build.
Wants it: creature-combo decks (Yawgmoth, Prossh), tokens/go-wide shells with lots of convoke fodder, and elf/devotion ramp decks that flood the board. Anything with silver-bullet creatures loves it.
Skip it in low-creature-count decks where convoke does nothing and you're paying full triple-green plus X — at that point you're better off with a cheaper tutor. It also whiffs if your deck lacks specific creatures worth fetching.
Related cards
Green Sun's Zenith
Tutors a green creature directly to the battlefield, scalable creature tutor.
Worldly Tutor
Cheaper green creature tutor, though only to hand.
Eldritch Evolution
Sacrifice-based creature tutor to battlefield in green.
Natural Order
Puts a green creature directly onto the battlefield.
Birthing Pod
Repeatable creature tutoring engine onto battlefield.
Tooth and Nail
Fetches creatures directly into play at instant-like impact.
Survival of the Fittest
Repeatable creature tutoring to hand for value.