Audio

Two rules: stream music, static effects. Load once, play many times.

local sounds = {}
 
function love.load()
  sounds.music = love.audio.newSource("assets/theme.mp3", "stream")
  sounds.music:setLooping(true)
  sounds.jump = love.audio.newSource("assets/jump.wav", "static")
  love.audio.play(sounds.music)
end
 
function playJump()
  -- clone for overlap: rapid jumps don't cut each other off
  local s = sounds.jump:clone()
  love.audio.play(s)
end

Volume + toggle

function love.keypressed(key)
  if key == "m" then
    local v = sounds.music:getVolume()
    sounds.music:setVolume(v > 0 and 0 or 0.8)
  end
end

Free sound sources: record with Audacity, generate with jsfxr, music from OpenGameArt (check licenses). Full list in Tools.

When it breaks

Symptom	Fix
Effect cuts off when replayed fast	:clone() before playing (above)
Music stutters / huge memory	Music must be "stream", effects "static" — swapped them?