What you have there will play three notes, one after another. To play them at the same time, put them each under their own Green Hat, then they will all start at the same time. You might also want to increase the play length, you have them all at zero beats which is really short.
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If you want the notes to play in the middle of the project, you probably will want to use the "When I Recieve" hat to start them all and then Broadcast them a message when you want them to start. The Green Hat is ususally used to start things at the beginning of the project.
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