integer tempo = 120,    -- beats per minute (max 800)
        measure = 4,    -- beats per bar
        runsecs = 5     -- total run time (rounded up to whole bars)

integer low_freq = #200, low_duration = 20,
        high_freq = #400, high_duration = 20

atom k32=0, xBeep
atom t0 = time(), count = 0
atom duration = 60/tempo,
     next = time()+duration

while time()<t0+runsecs do
    for j=1 to measure do
        if platform()=WINDOWS then
            if k32=0 then
                k32 = open_dll("kernel32.dll")
                xBeep = define_c_proc(k32, "Beep", {C_INT,C_INT})
            end if
            if j=1 then
                c_proc(xBeep,{high_freq,high_duration})
                if count=0 then t0 = time() end if
            else
                c_proc(xBeep,{low_freq,low_duration})
            end if
        else
            puts(1,7)
        end if
        count += 1
        puts(1,iff(j=1?"\nH":"L"))
        sleep(next-time())
        next += duration
    end for
end while
printf(1,"\naverage %f bpm\n",{count*60/(time()-t0)})