I have, in fact, used other music tools, including FamiTracker, which is also one of the best music tools ever. Also, I have an affinity for over-the-top statements.

No, the two players never have to be online at the same time to send their WarioWare DIY creations to each other. They merely need to add each other's Friend Codes first. Once both players have registered each other, there are two ways to transfer music:

a) On the DS version, you can access the Warehouse of any of your friends, and download any microgames, records, or comics that friend has stored. You can store up to two of each in your Warehouse for your friends to download.
b) On WarioWare DIY Showcase for the Wii, if any of your Wii contacts also have WarioWare DIY Showcase, you can send them your microgames, records, and comics. When you do, a yellow envelope will appear on their WarioWare DIY Showcase channel on the Wii menu. When they access the channel, they can then look at your creations and decide whether to keep them or not.

You never have to be online at the same time.

WarioWare DIY is one of the best music tools ever. Let's trade music with each other!

My DS Friend Code is 3009 1173 0734. To find your DS Friend Code, go to Distribution Center, and choose WFC, and choose Friend Settings. Your Friend Code will appear on the top screen. From this screen, you can also add other people's Friend Codes.

My Wii Number is 6324 9743 7460 3573. To find your Wii Number, go to Wii Message Board (envelope in the bottom right corner of the Wii menu), choose Create Message (second icon in the bottom left), and choose Address Book. Your Wii Number will appear. From this screen, you can also add other people's Wii Numbers. If the DIY Friend Notification Switch is ON in your Distribution Center on WarioWare DIY Showcase, then the game will automatically detect which people on your contact list also have WarioWare DIY Showcase, and allow you to exchange products.