Hi Mo,

Yes, ABC does handle a Bass clef. I have to say though, that ABC is one of those things (and it's not difficult) that you need to be reasonably proficient at to make much use of.

An example of Bass Clef from this dissussion:

X:1
T:Goldberg Variations no. 1
C:J.S.Bach
M:3/4
L:1/16
Q:360
V:2 bass
K:G
[V:1]GFG2- GDEF GAB^c |d^cd2- dABc defd |gfg2- gfed ^ceAG|
[V:2]G,,2B,A, B,2G,2G,,2G,2 |F,,2F,E, F,2D,2F,,2D,2 |E,,2E,D, E,2G,2A,,2^C2|

[V:1] FED^C DF[K:bass]A,G, F,A,D,2[K:treble] |z2d=c d2G2B,2d2 |z2ed e2A2C2e2|
[V:2] D,2F,E, F,2D,2 D,,2z =C, |B,,A,,B,,2- B,,D,E,F, G,A,B,G, |C,B,,C,2- C,E,F,G, A,B,CA,|

[V:1] z2fe f2d2a2c2- |c2B2 zGBd gdga |bgdB GBdg bgfe|
[V:2] D,^C,D,2- D,A,B,C [K:treble] DEFD |GFGD[K:bass] B,DG,B, D,G,B,,D, |G,,2G,2B,2G,2G,,2G,2|

[V:1] ae^cA FAce afed |gdBG EGBd gfed |^cGE^C A,CEG cedc|
[V:2] F,,2F,2A,2F,2F,,2F,2 |E,,2E,2G,2E,2E,,2G,2 |A,,2E,2G,2E,2A,,2G,2|

[V:1] d2[K:bass]F,2F,2[K:treble]A2d2f2 |B2[K:bass]G,2G,2[K:treble]B2e2g2 |^ceAG FAdf gedc |fd^cB AGFE D4 :|
[V:2] F,A,DF[K:treble] AFDA, [K:bass]F,A,D,F, |G,B,EG[K:treble] BGEB,[K:bass] G,B,E,G, |A,2^C2 DA,F,D, A,2A,,2 |D,,D,E,F, G,A,B,^C D4 :|

[V:1] fga2- abag fedc |Bcd2- dedc BAGF |E^GAB AEAB cA^de |
[V:2] D,,2F,E, F,2D,2D,,2F,2 |G,,2B,A, B,2G,2G,,2B,2 |C,2CB, C2F,2A,2C2 |

[V:1] fe^d^c B8- |B^de2- e^DE2- E[K:bass]^D,E,2[K:treble] |z^ga2- a^GA2- A^G,A,2-|
[V:2] A,2F,2 ^D,B,,D,F, B,^DFA |G3F G3F, G,3B,, |C,3[K:treble]B c3[K:bass]B, C3E,|

[V:1] A,B,CF B,^DEG FEDA |GFE^D EG[K:bass]B,A, G,B,E,2[K:treble] |z2e2c2e2a2A2|
[V:2]^D,2A,2G,2^A,,2B,,2F,2 |E,2G,F, G,2E,2 E,,2 z=D, |C,E,A,C ECA,E, C,E,D,C,|

[V:1] z2d2B2d2g2G2 |cAEC A,CEA cAce |fcAF DFAc fcfa|
[V:2] B,,D,G,B, DB,G,D, B,,D,C,B,, |A,,2C,2E,2G,2F,2E,2 |D,2F,2A,2C2B,2A,2|

[V:1] bgdB GBdg b=fbd' |ed'c'e dc'bd ce^fg |acBA BdBG cAGF |BGFE DCB,A, G,4 :|
[V:2] G,2B,2[K:treble]D2=F2E2D2 |C2E2^F2^G2A2=G2 |F2D2G2[K:bass]G,2D2D,2 |G,G,,A,,B,, C,D,E,F,G,4 :|