HO->SetAttenuation(1,1,20) allow to reduce metalic sound :
http://bochs.sourceforge.net/techspec/adlib_sb.txt

Bytes 40-55 - Level Key Scaling / Total Level

        7     6     5     4     3     2     1     0
     +-----+-----+-----+-----+-----+-----+-----+-----+
     |  Scaling  |             Total Level           |
     |   Level   | 24    12     6     3    1.5   .75 | <-- dB
     +-----+-----+-----+-----+-----+-----+-----+-----+

          bits 7-6 - causes output levels to decrease as the frequency
                     rises:

                          00   -  no change
                          10   -  1.5 dB/8ve
                          01   -  3 dB/8ve
                          11   -  6 dB/8ve

          bits 5-0 - controls the total output level of the operator.
                     all bits CLEAR is loudest; all bits SET is the
                     softest.  Don't ask me why.