Based on the documentation for yaps which is part of abcmidi, there is an alternative way that make work for some software. You can add octave=+2 or octave=-1 to the key/clef (K:) line or separately on an I: line.

X:1
K:C clef=bass octave=-2
ABcd

X:1
K:C clef=bass octave=-2
ABcd

Doesn't work here, apparently, but may be needed for certain software.

Based on the documentation for yaps which is part of abcmidi, there is an alternative way that may work for some software. You can add octave=+2 or octave=-1 to the key/clef (K:) line or separately on an I: line.

X:1
K:C clef=bass octave=-2
ABcd

X:1
K:C clef=bass octave=-2
ABcd

Doesn't work here, apparently, but may be needed for certain software.

Based on the documentation for yaps which is part of abcmidi, there is an alternative way that make work for some software. You can add octave+2 or octave-1 to the key/clef (K:) line or separately on an I: line.

X:1
K:C clef=bass octave=-2
ABcd

X:1
K:C clef=bass octave=-2
ABcd

Doesn't work here, apparently, but may be needed for certain software.

Based on the documentation for yaps which is part of abcmidi, there is an alternative way that make work for some software. You can add octave=+2 or octave=-1 to the key/clef (K:) line or separately on an I: line.

X:1
K:C clef=bass octave=-2
ABcd

X:1
K:C clef=bass octave=-2
ABcd

Doesn't work here, apparently, but may be needed for certain software.