Where can you find the poke flute in Pokemon Crystal?

The Flute doesn't exist in the Crystal version. However, you can find a program for your radio when you update it when the generator is fixed. After it is fixed, go to the radio tower located in Lavender (Not the Goldenrod one) and speak to a man inside. He will upgrade your Pokégear to let you listen to the programs in Kanto. One of them is the Pokéflute program.