update 2! Oceans14 writes: “If you are using this file patcher for New Super Mario Bros Wii, you don’t need to set any loop begin or end points in the BRSTM converter. Just make sure the “loop” box is checked in the converter, and make sure that the replaced BRSTMs and the BRSAR file are in the same folder. The BRSAR manager actually makes the BRSTMs loop for you.” Thanks Oceans14! :)
Update 1! White Dragon has released a BRSAR maker with multi-channel support (allowing Yoshi drums on a track). Check out the announcement post here.
To make custom music, download BCSM (Brawl custom Song Maker). You’ll also need Hamradio’s BSRAR Patcher* (info).

Open BCSM and click ‘Add…’, then ‘Add to Queue’, then select the MP3, WAV, OGG or FLAC file you want to use in NSMBw. You can choose multiple files if you want. When you’ve seleceted all the files you want to use, click ‘Convert to BRSTM’. The program will decode your music file, then encode it to BRSTM. It might pause for a while during this process, don’t worry if it does.

Go to your BCSM program folder and find a folder called ‘library’. Here you’ll find your converted song files, in BRSTM format. Just rename them to whatever music/audio file you want to replace in NSMBw, then put them in your Riivolution patch folder to use them (or inject them into your ISO). For a list of music files in the game and what they’re for, go here.
To make your songs loop properly, you need to patch your BRSAR file (found in the ‘Sound’ folder of your NSMbw ISO, download it here). Otherwise, your song will not loop properly because NSMB will think your file’s bigger/smaller than it actually is. You can edit the hex data by hand, or download Hamradio’s BSRAR Patcher* to make the job much easier. This guide will use the BSRAR Patcher method. Load the program and click ‘Open…’, then select your BRSAR file (‘wii_mj2d_sound.brsar’). Be sure to make a backup first, since this process will irreversibly edit the file.

Select the in-game music track you’ll be replacing (eg ‘Athletic’), then click the music file icon to select the music file you’ll be using to replace this track. Click the save icon (floppy disc) to save the new data to your BSRAR file. Put your newly edited BSRAR file in your Riivolution patch folder with the BRSTM music file you converted earlier, making sure the BSRTM is correctly named (eg, to ‘athletic_lr.n.32.brstm’). Now you can play NSMBw with your own soundtrack! Note that for multiple songs you don’t need multiple separately modified BSRAR files, just modify the same one multiple times, once for each song (find an example image here: the BRSAR file has been modified 19 times, once for each BRSTM).
To play BRSTM files, download the VGMStream plugin for Winamp. To view the old NewerSMBw music forum , go here, and to download Splashman’s NSMBw soundtrack rip, go here.
* Requires .Net framework 3.5
2001 copyright? What was this used for before the wii?
None of my songs loop, can someone help me?
Okay, so I've had a lot of trouble with this as well. If you are using this file patcher for New Super Mario Bros Wii, you don't need to set any loop begin or end points in the BRSTM converter. Just make sure the "loop" box is checked in the converter, and make sure that the replaced BRSTMs and the BRSAR file are in the same folder. The BRSAR manager actually makes the BRSTMs loop for you.
How does it know where to set the loop start and end points? if it just sets one at the end, that's really annoying, because i want to set my own loop points.