SCHG How-to

Change the SEGA Sound

From Sonic Retro

This guide targets the Hivebrain 2005 disassembly.

Changing the SEGA sound isn't like a simple rename .mp3 to .pcm. Instead, it's a lot more. But, I will show you how to change the SEGA chant in Sonic 1. You can replace it. There's a way.

Required Tools

The tools you will need is as follows:

An emulator (GENS, Kega Fusion, BlastEm)


Make the SEGA sound as high quality as possible

We need to make the SEGA sound as high quality as possible to continue with this tutorial, otherwise there'll be some Z80 format editing, and that's as complicated as can be. We don't want to get into that. Now, to make the SEGA chant slightly higher quality, follow this tutorial. Now open up your sonic1.asm file, and go to PlayPCM_Loop:. You should find this line:

move.w    #$14,d0     ; Write the pitch ($14 in this case) to d0

Change the $14 in the line to be $01. Now our SEGA sound will play at 27,025 Hz. The line should now look like this:

move.w    #$01,d0     ; Write the pitch ($14 in this case) to d0

Audacity Stuff

Head over to Audacity and grab a sound you like. For me, I'm using the Sonic CD extra life voice clip of Sonic saying "Yes!" Now, make sure these are specifications that are active: The project sample rate should be 27,025 Hz. The actual audio sample should be converted to 27,025 Hz, and then converted back to 41K or 48K Hz after you've made your changes. You have to convert it back, otherwise your audio will be very slow. Make sure that the audio is monophonic.

Now, save the file as follows: Set the file type to "Other uncompressed files" and set the file format as .RAW. Make sure the header is RAW and that it's header-less. Make sure that the encoding is an unsigned 8-bit PCM.

Save the file into the sound folder of the disassembly. Now to change the code to actually play your custom sound.

Making Sonic 1 play the sound

Head to the end of "sonic1.asm" and you should find this somewhere:

SegaPCM:    incbin    sound\segapcm.bin
SegaPCM_end:    even

Replace segapcm.bin with whatever your file name is. And bravo! You should have your new SEGA sound. Ciao!

SCHG How-To Guide: Sonic the Hedgehog (16-bit)
Fixing Bugs
Fix Demo Playback | Fix a Race Condition with Pattern Load Cues | Fix the SEGA Sound | Display the Press Start Button Text | Fix the Level Select Menu | Fix the Hidden Points Bug | Fix Accidental Deletion of Scattered Rings | Fix Ring Timers | Fix the Walk-Jump Bug | Correct Drowning Bugs | Fix the Death Boundary Bug | Fix the Camera Follow Bug | Fix Song Restoration Bugs | Fix the HUD Blinking | Fix the Level Select Graphics Bug | Fix a remember sprite related bug
Changing Design Choices
Change Spike Behavior | Collide with Water After Being Hurt | Fix Special Stage Jumping Physics | Improve the Fade In\Fade Out Progression Routines | Fix Scattered Rings' Underwater Physics | Remove the Speed Cap | Port the REV01 Background Effects | Port Sonic 2's Level Art Loader | Retain Rings Between Acts | Add Sonic 2 (Simon Wai Prototype) Level Select | Improve ObjectMove Subroutines | Port Sonic 2 Level Select
Adding Features
Add Spin Dash ( Part 1 / Part 2 / Part 3 / Part 4 ) | Add Eggman Monitor | Add Super Sonic | Add the Air Roll
Sound Features
Expand the Sound Index | Play Different Songs Per Act | Port Sonic 2 Final Sound Driver | Port Sonic 3's Sound Driver | Port Flamewing's Sonic 3 & Knuckles Sound Driver | Change The SEGA Sound
Extending the Game
Load Chunks From ROM | Add Extra Characters | Make an Alternative Title Screen | Use Dynamic Tilesets | Make GHZ Load Alternate Art | Make Ending Load Alternate Art | Add a New Zone | Set Up the Goggle Monitor | Add New Moves | Add a Dynamic Collision System | Dynamic Special Stage Walls System | Extend Sprite Mappings and Art Limit | Enigma Credits | Use Dynamic Palettes
Convert the Hivebrain 2005 Disassembly to ASM68K
Split Disassembly Guides
Set Up a Split Disassembly | Basic Level Editing | Basic Art Editing | Basic ASM Editing (Spin Dash)

Written by XPointZPoint