Linux Multimedia Studio (LMMS) is a free DAW (digital audio workstation) created for Linux & Windows. Although it has a rather steep learning curve, there are many tutorials and it includes several sample songs that you can learn from. Users learn the functions pretty quickly once they go through a few of the examples.
LMMS allows the user to create and produce music by synthesizing sounds, arranging samples and playing on a MIDI keyboard. Features include trackers, sequencers, synthesizers and a beat/bassline editor. It also has a song editor to help organize materials into larger forms and a piano-roll window to aid in writing MIDI parts.
This DAW also lets you add effects to pre-existing audio so that you can record something and import it as a sample. You can add filters, distortion or any other effects you like and then make the whole file one track. By creating samples in the same composition program you can save a lot of time that you would normally waste by copying it between multiple programs.
The piano roll previously mentioned allows easy editing by clicking on the right pitch at the right time and clicking to insert the note. The note value can easily be changed by resizing it with the mouse.
One drawback of LMMS is that it has no "undo" function anywhere in the program. That can be quite frustrating but as you learn the program better you probably won't miss it.
LMMS come equipped with four different synthesizers. There is one that allows manipulation of samples by adding filters and a BitInvader plugin that is a wavetable synthesizer, allowing you to create a waveform for your sound. There is a guitar synthesizer and one with three oscillators. Most of LMMS's controls are understandable but you can get guidance by right clicking and selecting the "help" option.Go there...