Here are the meanings of the values for ATTACK, DECAY, and RELEASE:

VALUE	ATTACK RATE (TIME/CYCLE)	DECAY/RELEASE RATE (TIME/CYCLE)
0	2 ms	6 ms
1	8 ms	24 ms
2	16 ms	48 ms
3	24 ms	72 ms
4	38 ms	114 ms
5	56 ms	168 ms
6	68 ms	204 ms
7	80 ms	240 ms
8	100 ms	300 ms
9	250 ms	750 ms
10	500 ms	1.5 s
11	800 ms	2.4 s
12	1 s	3 s
13	3 s	9 s
14	5 s	15 s
15	8 s	24 s

Here are a few sample settings to try in your example program. Try these and a few of your own. The variety of sounds you can produce is astounding! For a violin type sound, try changing line 20 to read:

   20 POKES+5,88:POKES+6,89:REM A=5;D=8;S=5;R=9

Change the waveform to triangle and get a xylophone type sound by using these lines:

   20 POKES+5,9:POKES+6,9:REM A=0;D=9;S=O;R=9
   70 POKES+4,17
   90 POKES+4,16:FORT=1TO50:NEXT