While all of the evil credit of course goes to you, I feel that I have made some neat* modifications:

signal = []
t=0L
pscale=5
pexp=2
transpose = 0
iterations = 10
for ii in range(1,iterations):
    for (p,d) in [(4,1),(5,1),(7,3),(None,1), (4,1),(5,1),(7,3),(None,1), (4,1),(7,1),(12,2),(11,2),(9,2),(9,2),(7,1),(None,1), (2,1),(4,1),(5,3),(None,1), (2,1), 
(4,1),(5,3),(None,1), (2,1),(5,1),(11,1),(9,1),(7,2),(11,2),(12,4)]:
        if p is not None: 
            add_note(t, random.choice([440*2**(((p+transpose)+random.choice([-1,0,0,0,1]))/12.),440*2**(((p+transpose)+random.random())/12.)]), 0.3*d+0.1, 1)
        t += 0.3*d*math.exp(random.random()*random.random())
    transpose = random.choice([-14, -9, -7, -4.5, -2, -1, 0, 0.5, 1, 2, 4.5, 7, 9, 14]) #transpose up or down
    t += 5*(pexp*((pscale**pexp)/((random.randrange(200,600,1)/100)**(pexp+1)))) #wait a while before repeating
save_signal()

*Where neat is, of course, a synonym for evil