Linux Multimedia Studio (LMMS) is an open source application that lets you create music. It includes a song editor for composing, a bassline editor, a tool for editing melodies and patterns, an FX mixer, and numerous other music features.
Here's how you can install LMMS in Ubuntu 14.04.
1. Open a terminal window.
2. Type in the following commands then hit Enter after each:
sudo add-apt-repository ppa:irie/lmms
sudo apt-get update
sudo apt-get install lmms
Source: Noobs Lab
Additional resources for LMMS
Additional Ubuntu resources