So I've recently come across a very nice tab interface, for those who don't know, it's the one that looks like the one below:

I have all the componentIds and all the childIds. Note you will need to use an interface editor to get rid of the "Exit" text, as it's already printed on that button (use a hex editor).
Anyway, here's the code:
InterfaceManager.java
Find
Code:
sendTab(125, 187); // music
Replace with
Code:
sendReplacedMusicTab();
Find
Code:
sendTab(185, 187);// music
Replace with
Code:
sendReplacedMusicTab();
Code:
public void sendReplacedMusicTab() {
sendTab(resizableScreen ? 125 : 185, 1247);
player.getPackets().sendIComponentText(1247, 0, "1");//1
player.getPackets().sendIComponentText(1247, 21, "2");//2
player.getPackets().sendIComponentText(1247, 32, "3");//3
player.getPackets().sendIComponentText(1247, 43, "4");//4
player.getPackets().sendIComponentText(1247, 54, "5");//5
player.getPackets().sendIComponentText(1247, 65, "6");//6
player.getPackets().sendIComponentText(1247, 65, "7");//7
}
ButtonHandler.java
Code:
else if (interfaceId == 1247) {//Custom music tab buttons
switch(componentId) {
case 9://1
break;
case 18://2
break;
case 29://3
break;
case 40://4
break;
case 51://5
break;
case 62://6
break;
case 71://7
break;
}
}