Each note of the flute mimics the call of a different beast.

Tenth Edition

Citanul Flute

{X}, {T}: Search your library for a creature card with converted mana cost X or less, reveal it, and put it into your hand. Then shuffle your library.

{X}, {T}: Search your library for a creature card with mana value X or less, reveal it, put it into your hand, then shuffle.

Urza's Saga

o
X, oc
T: Search your library for a creature card with total casting cost no greater than X. Reveal that card and put it into your hand. Shuffle your library afterward.