Network related extensions:
Apple Enet 2.4.5, AppleShare 3.9.4, Open Transport 2.8.3, Open Transport ASLM Modules 2.8.3, Shared Library Manager PPC 2.0.2, Internet Config Extension 2.0.7
USB/FireWire related extensions:
FireWire Enabler 2.8.7, FireWire Support 2.8.7, HID Library 1.5.9, USB Device Extension 1.5.9
QuickTime And Sound Manager related extensions:
Apple Audio Extension 2.4, Sound Manager 3.7.1, QuickTime Extensions, QuickTime 6.0.3, QuickTime Musical Instruments 6.0.2, QuickTime  PowerPlug 6.0.3
OpenG related extensions:
OpenGLEngine 1.2.4, OpenGLLibrary 1.2.5, OpenGLMemory 1.2.4, OpenGLRenderer 1.2.4, OpenGLUtility 1.2.4
Video card related extensions:
NVIDIA 2D Acceleration 3.5.2, NVIDIA Drive 3.5.2, NVIDIA DVD Accelerator 3.5.2, NVIDIA Engine 3.5.2, NVIDIA OpenGL 3.5.2, NVIDIA Video Accelerator 3.5.2
Other Extensions:
DrawSprocketLib 1.7.8, InputSprocket Extension 1.7.3, Time Synchronizer 8.3.3, Contextual Menu Extension 1.0.2, Joliet Volume Access 2.1b5,
Text Encoding Converter 1.6, Apple CD/DVD Driver 1.4.8, DVD Region Manager 1.1, CarbonLib 1.6.1, Multiprocessing 
Control Panels:
Joliet Control 2.1b5,USB Overdrive 1.4,Appearance 1.1.4,Date & Time 8.3.3, Energy Saver 3.0.5,File Exchange 3.0.5, General Controls 8.0.3, Internet 1.0.3, Keyboard 8.6.2,Memory 8.1.3,Monitors 7.5.6, Numbers7.1,QuickTime Settings 6.0.2, Sound      8.5.8, Startup Disk 9.2.6,TCP/IP 2.5,Text  8.0
I will not explain the function of every control panel and extension here, you can google something if you are curious or use this as a quick start guide and take the advice on pure faith...
1) INITIAL TWEAKS
- Memory ControlPanel
From the Apple Menu, choose the “Control Panels” pop-up, and click MEMORY
Turn Virtual Memory OFF
Be Sure RAM DISK is OFF.
- Energy Saver Control Panel
From the Apple Menu, choose the “Control Panels” pop-up, and click ENERGY SAVER
In the SLEEP SETUP page, set “Put the system to sleep” at NEVER.
(It is also recommended that the SLEEP command not be used from the "Special" menu)
- Disable Appletalk
From the Apple Menu, click CHOOSER
Click INACTIVE in next to the Appletalk option at the bottom right corner of the window.
- Disable Font Smoothing
From the Apple Menu, choose the “Control Panels” pop-up, and click APPEARANCE
Click the FONTS tab inside the Appearance window.
Disable the option “SMOOTH ALL FONTS”
2) VIDEO CARD INFORMATION (needed for later on)
From the Apple Menu, click "Apple System Profiler"
Select the Second Tab at the top "Devices and Volumes"
Under the PCI, Slot-1, AGP section, click the blue triangle to the left of "Display Card" to open the Video card info. write down the card Manufacturer
3) EXTENSIONS AND CONTROL PANELS
Trim your Extensions & Controls Panels to help performance and prevent possible extension conflicts; if you are a Newbie to OS 9, when in doubt, don't turn off an extension unless you are sure you don't need it, the amount of RAM saved is not worth the headache you are going to have if you inadvertently turned off something you need and don't realize it...if you want to experiment, you can use this guide first as a baseline and then pick "Duplicate Set" and try variations of your initial modified setup, that way, you can easily switch back if you make a mistake
From the Apple Menu, choose the “Control Panels” pop-up, and click EXTENSIONS MANAGER..
Click “Duplicate Set” at the bottom right corner of the Extensions Manager window. Name the duplicate set when prompted… something like "Recording Studio Mac" or your name as an Artist or Production Company
Sort First... it will make the below list much easier !
Click on the word "Package" at the top of the Package column to immediate sort the Control Panels and Extensions, this will immediately give you a bird's eye view of which packages belong together
- Control Panels to turn off
If you don't intend on using a dial-up telephone modem..
Remove the X from
     DialAssist
     Modem
     Remote Access
Also, Remove the X from
     Location Manager
     Multiple Users (assuming you are the only user, you better be, don'y let anyone use your Music Mac)
     Software Update
     USB Printer Sharing (who likes to share anyway)
     Web Sharing
- Extensions to turn off
If you don't have an Airport Wireless Card Installed...
Remove the X from
     Airport AP
     Airport AP Support
     Airport Driver
If you don't access your Mac remotely...
Remove the X from
     OpenTpt Remote Access
     OpenTpt Serial Arbitrator
     Remote Only
If you don't Voice Control your Mac...
Remove the X from
     Speech Recognition
If you use iTunes, but don't own a Nomad, SoundSpace, or Rio (I don't think you own any of these)...
Remove the X from
     Nomad II USB Driver
     Nomad MG USB Driver
     Nomad USB shim
     NomadJukeboxLib
     SoundSpace2Lib
     NomadJukeboxLib Driver
     USBRioDriver
     USBSoundSpace2 Driver
To turn off hard drive file indexing (trust me, you want it off)
Remove the X from
     FBC Indexing Scheduler
No Zip or Jaz drive ?
Remove the X from
     Iomega Drive
Some to trust me on... unless you know otherwise
Remove the X from
     Location Manager Extension
     Multi-User Startup
     Serial Tool
     Software Update Engine
     Software Update Scheduler
     Voice Verification
     VT102 Tool
     XMODEM Tool
     Web Sharing Extension
     Setup Assistant API
     Setup Assistant Launcher
     Setup Info Dispatcher
     Setup Internet Support
     Setup Modem Selector
To turn off un-needed video extensions (remember you found out your video card in Step 2
If you have an nVidia Card
Remove the X from
     All Extensions with "ATI" in them
If you have an ATI Card
Remove the X from
     All Extensions with "nVidia" in them
4) ADVANCED TRICKS & TIPS:
After an Initial Mac OS 9 Install navigate to the Extensions folder in the System Folder, select all the files (hold down Command/Apple and press 'A'), and label them with a color. This way, any third-party extensions added subsequently are easy to spot since they will appear with a different color to the original set and these colours will be visible in Extensions Manager!.