LMMS is a free cross-platform software which allows you to produce music with your computer. This covers creating melodies and beats, synthesizing and mixing sounds and arranging samples. You can have fun with your MIDI keyboard and much more – all in a user-friendly and modern interface. Furthermore LMMS comes with many ready-to-use instrument and effect plugins, presets and samples.
LMMS is in the offical Archlinux repository, but you may also need the git "master branch" version for the newest improvements.
Where is VeSTige ?
If VST support won't work on x86_64 systems, you can always build lmms-git from AUR with the melchips's vst fix patch(https://bbs.archlinux.org/viewtopic.php?id=166627).