After you collect coins at Midas River, you arrive in Mallow's home, Tadpole Pond.

Visit Tadpole Pond

After you complete the Midas River minigame, you can continue on to Tadpole Pond.

Go northeast and stand on the rock in front of the pond. There will be a cutscene. When the tadpoles stop to watch Mario jump, press the jump button to continue.

Afterward, jump across the tadpoles, and there will be another cutscene. You can ask Frogfucius to repeat himself if you wish.

After that, talk to Frogfucius, and if you got the Cricket Pie by talking to the shopkeeper in Mushroom Kingdom, he will give you the FroggieStick, a weapon for Mallow.

Then go southwest and jump across the tadpoles again.

You can optionally go northwest and talk to the two tadpoles. One shop is only available to cardmembers, but you can buy FroggieDrink without a card. The other shop allows you to exchange Frog Coins for items.

If you go southeast, you find Melody Bay. You can go northeast to find a save block, and you can go west from the save block to talk to Toadofsky. He can give you a lesson on composing music. He shows you which lines in the pond correspond to which notes:

     Re    Ti    So
| Mi || Do || La || Fa |

If you checked on the scroll near Frogfucius or talked to the tadpole near the entrance to Melody Bay, you will have seen the song
So La Mi Re Do Re Do Re
You can walk onto the rock at the southwest side of Melody Bay and jump when the tadpole has stopped where you want. The tadpole will stay there and another will appear to the northeast. Stop the tadpoles at the lines that you want, and you can compose a short song. If you play So La Mi Re Do Re Do Re, Toadofsky gives you an Alto Card. You can now go back to the shop in the northwest part of Tadpole Pond, where they have added Elixir to the list of items to purchase from the cardmember shop, and FroggieDrink is now two coins cheaper.

There will be other songs that you can play at Melody Bay, so be sure to keep an eye out for more music.

When you are ready to move on, exit Melody Bay the way that you came in, then use the southwest exit to leave Tadpole Pond. Then you can continue on to Rose Way.