By building the String Synth project, I've noticed that the envelope module had attack and decay way too fast.
So, I've rebuild one envelope bit and changed a resistor ( blue circle )and a capacitor ( yellow circle ).
I've changed the resistor into 120 Ohms instead of 100 Ohms
The capacitor changed from 1uF to 4.7uF.
These parts can be obtained via online electronic parts stores.
Now, the attack at max. has 4 seconds ( original was 1 sec. ), the delay becomes now 12 sec. ( original was 3 sec. ).
You can hear these slow attacks and decays throughout the song I've composed in the Synth String project. They can also be heard in the slow moving noise waves.
You need a steady hand and magnifying glasses to solder them though