Oops, my idents disappeared. I'll insert some brackets:

$4008 write:
LinearCounterLoad = data & 0x7F
if (LinearCounterMode == LOAD)
{
LinearCounter = LinearCounterLoad
}

$400A write:
TimerLoad.low = data
Timer = TimerLoad

$400B write:
LengthCounter = LengthCounterTable[data >> 3]
TimerLoad.high = data & 7
Timer = TimerLoad
LinearCounterMode = LOAD
LinearCounter = LinearCounterLoad
ChangeMode = ($4008.7 == 0)

LinearClock:
if (LinearCounterMode == COUNT && LinearCounter)
{
LinearCounter--
}

if (ChangeMode)
ChangeMode = 0
if ($4008.7 = 0)
{
LinearCounterMode = COUNT
}

LengthClock:
if (LengthCounter && ($4008.7 = 0) && ($4015.2 = 0))
{
LengthCounter--
}

TriangleStepGenerator:
Timer = TimerLoad
if (($4015.2 = 0) && LinearCounter && LengthCounter) /* channel enabled? */
{
if (Output == 0xF) step--
if (Output == 0x0) step++
output += step
}