Browsing the net I found this post on connecting the chip to a Dragon computer. It also includes a sample BASIC program to test the chip is working and I think it should easily convert to C++ on the Arduino to see if you get the same results. If not then maybe you need to look at your code sequence/timings for writing to the chip and maybe the pinout.
Sample Programs
The first program producing some warbling noises across both channels
(if you connect the device up to a stereo system, you should hear it switch channels)
and the second one creates a tone, which sounds like the hard drive on a PC taking off.
I have included these more as a systems check to ensure your device is working rather as good examples of how to use it.
1 HD=1
10 _DATA=&HFF3C 'DATA REGISTER - MACHINE SPECIFIC
20 _ADDR=&HFF3D 'ADDR REGISTER - MACHINE SPECIFIC
21 POKE _ADDR,20:POKE _DATA,3 'FREQUENCY 0,1 ENABLE (REG &H14)
22 POKE _ADDR,9:POKE _DATA,200 'FREQUENCY OF TONE 1 = 200 (REG &H09)
23 POKE _ADDR,&H15:POKE _DATA,0 'NOISE DISABLE (ALL CHANNELS)
24 POKE _ADDR,&H10 'ETC,
25 POKE _DATA,&H23 'ETC
26 POKE _ADDR,&H11
27 POKE _DATA,&H04
30 POKE _ADDR,0
40 POKE _DATA,&H77
50 POKE _ADDR,28
60 POKE _DATA,1
65 POKE _ADDR,8
70 POKE _ADDR,20:POKE _DATA,&H43
85 F=100
88 FD=3
100 G=15
105 GD=45
110 FOR H=&H11 TO &H44 STEP &H11
111 F=F+FD:IF F>240 OR F<10 THEN F=240:FD=-FD
115 G=G+GD:IF G>230 OR G=15 THEN GD=-GD
116 POKE _ADDR,0:POKE _DATA,G
117 POKE _ADDR,1:POKE _DATA,G
118 POKE _ADDR,17:POKE _DATA,(&H55-H)
120 POKE _ADDR,16
130 POKE _DATA,H
131 POKE _ADDR,8:POKE _DATA,F:POKE _ADDR,9:POKE _DATA,F+10
135 WAIT 50
140 NEXT
150 FOR H=&H44 TO &H11 STEP -&H11
151 F=F+FD:IF F>200 OR F<10 THEN F=200:FD=-FD
155 G=G+GD:IF G>230 OR G=15 THEN GD=-GD
156 POKE _ADDR,0:POKE _DATA,G
157 POKE _ADDR,1:POKE _DATA,G
158 POKE _ADDR,17:POKE _DATA,(&H55-H)
160 POKE _ADDR,16
170 POKE _DATA,H
171 POKE _ADDR,8:POKE _DATA,F:POKE _ADDR,9:POKE _DATA,F+55
175 WAIT 50
180 NEXT
190 GOTO 110
NIMBUS.BAS
----------
10 _DATA=&HFF3C
20 _ADDR=&HFF3D
30 POKE _ADDR,2:POKE _DATA,255
40 POKE _ADDR,10:POKE _DATA,100
50 POKE _ADDR,&H11:POKE _DATA,4
60 POKE _ADDR,&H14:POKE _DATA,4
70 POKE _ADDR,&H15:POKE _DATA,0
75 POKE _ADDR,&H18:POKE _DATA,11
80 POKE _ADDR,&H18:POKE _DATA,139
90 POKE _ADDR,28:POKE _DATA,1
100 POKE _ADDR,9:POKE _DATA,0
110 POKE _ADDR,&H10:POKE _DATA,64+16
115 POKE _ADDR,&H14:POKE _DATA,0
120 FOR G=255 TO 1 STEP -4
130 POKE _ADDR,9:POKE _DATA,G
135 WAIT 50
140 NEXT