Powershell, 184 120 bytes

for($d='0;?3,>5:.H7<1/9@E42-6B8CG='[$args[0][0]-65]-42;$d-1){[Console]::Beep(880,200*($d%2*3+1))
$d=$d-shr1
sleep -m 70}

Test script:

$f = {

for($d='0;?3,>5:.H7<1/9@E42-6B8CG='[$args[0][0]-65]-42;$d-1){[Console]::Beep(880,200*(($d%2)*3+1))
$d=$d-shr1
sleep -m 70}

}

&$f "A"
sleep -m 700
&$f "B"

I used a timing setup for beginers:

• the dot duration is 200ms
• the gap between elements is less then dot duration (70 ms)
• the dash duration is 4 dot durations