Musical Secrets: Bonus Track 2

Difficulty: 2.5 of 5
Area: 1.5 of 5
Cache-Size: big
Coordinates: N 52° 24.243 E 009° 41.165
Position: North/East
Musical Secrets: Bonus Track 2
Part of the GeoTour "Ge(o)heimnisse der Region Hannover"
The cache is not at the specified coordinates. To find the cache you have to complete the following caches first:
Musikalische Ge(o)heimnisse: Instrumente
Musikalische Ge(o)heimnisse: CD
Musikalische Ge(o)heimnisse: Live
You will find a bonus word in each of them - the first letter must be converted into a number.
Those three digits in the order listed above will open the first lock!
In order to get at the logbook, you have to do a few more things. What German cities are those three songs about? The first letter of each city has to be converted into a number. Calculate the digit sum if the letter has more than one digit.
Attention: you might want to research songs for the ten largest cities in Germany before you attempt this cache.
BONUSCODE: _ _ _
To get the bonus number, you have to calculate a single digit sum.