What is LMMS anyway?
LMMS is part of a family of softwares known as digital audio workstations, or DAWs. It is a sound generation system, synthesizer, beat/bassline editor and MIDI control system that can power an entire home music studio. With LMMS, sounds and tones can be generated, played, and artfully arranged to create entire tracks with ease. The tools needed to arrange sounds and rhythms to create tracks, layer tracks to create songs, and save songs to an output format are all there, ready for you to use. With a MIDI keyboard, you can also play your music live while composing or performing.
Is LMMS comparable to any commercially available software?
Users may find LMMS has much in common, at least in principle, with Apple's Garage Band, FL Studio (formerly Fruity Loops), Logic Studio, Beat Machine Pro and similar powerful audio tools. In terms of capability, LMMS easily matches the lower to middle-tier professional software available. This makes LMMS a great introduction to audio production. LMMS is also constantly developing.
Is LMMS offered in my language?
Is it free?
Yes. LMMS is free and open source. This means that as long as there are people coding for LMMS on their own free time, LMMS will become better and better!

2.1.2 Usage

How do I create an instrument track in the Beat/Bassline Editor?
Drag it in from the sidebar as you would with the Song Editor! You can open My Samples or My Presets (buttons on the far left side of the window) and double click on the preset to get it there too.
How do I change the note an instrument plays in the Beat/Bassline Editor?
Click on the instrument button on the track. There's a green bar just above the keyboard at the bottom, an orange square indicates the key that is played. Click on the blue bar to change the note.
How do I enable and adjust looping points?
Click on the enable/disable loop points button in the song editor or piano roll. It is disabled by default. Two blue arrows will appear in the upper tracking area of the window. You can adjust these loop points by right-clicking and dragging them or pressing middle and right button.
I made some piano chords in the Song-Editor but now I want to loop them. How to get them to the Beat+Bassline Editor?
Simply hold Ctrl while dragging the instrument handle into the Beat+Bassline Editor. Only the first pattern will follow.
How do I import a drums beat I'd made in Hydrogen?
As of LMMS 0.4.14, you can import your Hydrogen file directly into LMMS. If you exported it as a MIDI, it can be easily imported with Project > Import. Remember to specify a SoundFont file! If on the other hand, you exported it to WAV, you'll have to use the AudioFileProcessor plugin and import it from there. You can import your MIDI the same way too.
How do I import a FLAC, WAV or OGG file?
Through the AudioFileProcessor plugin.
Can I sell my song that I made in LMMS?
Yes. As long as you have just used samples, instruments and effects from LMMS, or know that the external material has correct licenses, you can sell your song created in LMMS.
How do I edit the locations in the sidebar when you open a file in LMMS?
Highlight the folder that you want to be on the sidebar, select it, and drag it to the sidebar.
What do I do when it is pops and clicks at the beginning or end of a note?
Turn up the attack or the release knob.

2.1.3 Settings

I want to use another soundcard than the default one with LMMS. How to achieve this?
It's recommended to set your preferred audio-interface and it's parameters using the setup-dialog. If this doesn't work for some reason, you can also set the environment-variable "AUDIODEV" to whatever your audio-device is (e.g. /dev/dsp for OSS or surround40:1,0 for ALSA).
I want to import MIDI files but it tells me I need to specify a default soundfont?
First download a soundfont for free from the internet. Then in LMMS go to Edit > Settings > Paths (folder icon). Under the "default soundfont file"-section, you can browse for the downloaded file.