smconv turns music written in a tracker — Impulse Tracker .it modules — into a SNESMOD soundbank: the packed music, samples, and effect data the SPC700 plays. It is how you get real, multi-channel music (and sound-effect banks) into a game, driven from C by a few snesmod* calls (snes/snesmod.h).

What goes in, what comes out

In: one or more .it files (each becomes a numbered module — songs and/or SFX banks).

Out (soundbank mode, -s):

File	What it is	Used by
<base>.asm	the soundbank data (assembled into the ROM)	the build
<base>.h	C constants for each module and effect	your game code
<base>.brr	the BRR sample data	the soundbank

Without -s, smconv instead writes a single standalone .spc you can play in an SPC player — handy for auditioning a module outside the SDK.

How you actually use it

You almost never call smconv directly. Declare it in the example Makefile and the build runs it with the right OpenSNES conventions:

USE_SNESMOD := 1

SOUNDBANK_SRC := music/mysong.it # one or more .it files

Under the hood that becomes:

smconv -s -o soundbank -b 1 -n -p soundbank music/mysong.it

Then, in C, load and play by module number (the .h gives you the names):

snesmodInit();
snesmodSetSoundbank(SOUNDBANK_BANK);
snesmodLoadModule(MOD_MYSONG);            // load a module
u8 jump = snesmodLoadEffect(SFX_JUMP);    // load an effect, keep its slot
snesmodPlay(0);                           // play from pattern 0
 
/* in the game loop */
snesmodPlayEffect(jump, 127, 128, SNESMOD_PITCH_NORMAL); // volume, pan, pitch
snesmodProcess();                         // once per frame

examples/games/likemario does exactly this. (spcLoad / spcPlay are the PVSnesLib names — see Migrating from PVSnesLib.)

See Audio & Music Tutorial and SNES Sound Programming Guide for the runtime side.

The flags behind the Makefile

Flag	Meaning
-s	soundbank mode (the game path; default is standalone .spc)
-o FILE	output base name (required in soundbank mode)
-b N	ROM bank for the soundbank data — OpenSNES uses 1 (SNESMOD default is 5)
-n	skip the hdr.asm include — required in OpenSNES
-p NAME	symbol prefix (OpenSNES sets it to the output base)
-f	check .it sizes against the first file (for SFX banks)
-i	HiROM mapping · -V verbose (reports SPC RAM usage)

Gotchas worth knowing up front

Declare, don't invoke. For a game build, set USE_SNESMOD and SOUNDBANK_SRC; the bank (-b 1), no-header (-n) and prefix flags are OpenSNES-specific and the Makefile gets them right. Calling smconv by hand with SNESMOD's defaults will not link.
Many modules, one bank. Pass several .it files to get several modules — music via snesmodLoadModule(N) + snesmodPlay(0), effects via snesmodLoadEffect(N) + snesmodPlayEffect(slot, …).
SPC700 limits are real. Up to 8 channels; samples auto-convert to BRR at 32 kHz max; -V reports how much of the SPC's 64 KB you are using — watch it, because music and samples share that space.
HiROM builds relocate the soundbank origin (the build handles the .ORG fix-up for you).

See it in practice

SNESMOD Music Example — a full song playing.
SNESMOD Sound Effects — a sound-effect bank.
LikeMario and Tetris — music and SFX in real games.

For a single one-shot sample rather than a whole module, use wav2brr — WAV to BRR sound samples — it shares smconv's BRR encoder, so the samples sound identical.