Though linux has many different music programs out there and even distributions that are completely designed around music and video production like studio ubuntu. Though one easy program for making drum beats and what not is Hydrogen drum machine. Hydrogen is a great and easy to start and pick up.
Hydrogen is a GUI built program so you don't need to worry about command line program for making beats. Some of the features that they have are:
Pattern-based sequencer, with unlimited number of patterns and ability to chain patterns into a song.
Up to 192 ticks per pattern with individual level per event and variable pattern length.
Unlimited instrument tracks with volume, mute, solo, pan capabilities.
Multi layer support for instruments (up to 16 samples for each instrument).
Sample Editor, with basic cut and loop functions. (NEW)
Time-stretch and pitch functions via rubberband cli. Require the rubberband-cli package. (NEW)
Play-lists with scripting function. (NEW)
Advanced tab-tempo. (NEW)
Director Window with a visual metronome and song position tags. (NEW)
Time-line with variable tempo. (NEW)
Single and stacked pattern mode. (NEW)
Export/Import single patterns into song projects. (NEW)
Midi learning via Shift+MouseClick on many gui-cotrollers combined with a midi settings editor. (NEW)
Ability to import/export song files.
Unique human velocity, human time, pitch and swing functions.
Multiple patterns playing at once.
If your looking for a easy to use free drum machine don't worry linux has you covered with hydrogen.
I highly encourage that program as it is simple and is easy for even someone that does not know much about music to even use.
local tech repair admin