BM* format. I wrote this for myself so it may be a bit hard to understand. :)
BMW is just like BMX except it doesn't include the 'WAVE' section.

Header:

Type/Size	Description
-------------------------------------------------------------------------
4  			"Buzz"
dword		number of sections
12*31		up to 31 section dir entries

=========================================================================

Section dir entry:

Type/Size	Description
-------------------------------------------------------------------------
4			four-char name of section
dword		offset from begin of file
dword		size in bytes

=========================================================================

Section 'MACH' - machines

Type/Size	Description
-------------------------------------------------------------------------
word		number of machines

(first machine - always master)
asciiz		name 
byte			type (0 = master, 1 = generator, 2 = effect)
asciiz		name of DLL if type is 1 or 2
float		X coordinate in machines view [-1..1]
float		Y coordinate in machines view [-1..1]
dword		size of machine specific data
x			data
word		number of attributes

(first attribute)
asciiz		key
dword		value

(second attribute)
...

x			state of global parameters
word		number of tracks 
x			state of track parameters for each track

(second machine)
...

=========================================================================

Section 'CONN' - machine connections

Type/Size	Description
-------------------------------------------------------------------------
word		number of connections

(first connection)
word	 	index of source machine
word		index of destination machine
word		amp
word		pan

(second connection)
...


=========================================================================

Section 'PATT' - patterns for each machine 

Type/Size	Description
-------------------------------------------------------------------------
(first machine)
word		number of patterns
word		number of tracks

(first pattern)
asciiz		name 
word		length of pattern in number of ticks (rows)
x			pattern data

(second pattern)
...

(second machine)
...

=========================================================================

Section 'SEQU' - pattern sequences 

Type/Size	Description
-------------------------------------------------------------------------
dword		end of song 
dword		begin of loop
dword		end of loop	
word		number of sequences

(first sequence)
word		index of machine
dword		number of events
byte		bytes per event pos 
byte		bytes per event (2 if there are more than 112 patterns)
x			event list (pos, event, pos, event, pos, event...). events:
				00 = mute, 01 = break, 02 = thru
				0x10 = first pattern, 0x11 = second pattern, etc.
				msb=1 indicates loop

(second sequence)
...

=========================================================================

Section 'WAVT' - wavetable 

Type/Size	Description
-------------------------------------------------------------------------
word		number of waves

(first wave)
word		index
asciiz		full file name, e.g. "c:\waves\blah.wav"
asciiz		name
float		volume 
byte		flags:
				bit 0: loop
				bit 1: don't save
				bit 2: floating point memory format
				bit 7: envelopes follow (since alpha 14)  

if flag bit 7 --------->
	word		number of envelopes 
	
	(first envelope)
	word		Attack time
	word		Decay time
	word		Sustain level
	word		Release time
	byte		ADSR Subdivide
	byte		ADSR Flags: 0-1 = attack mode, 2-3 = release mode, 4 = linear decay, 5 = sustain
		
	word		number of points (can be zero) (bit 15 set = envelope disabled)
	
	(first point)
	word		x 
	word		y 
	byte		flags: bit 0 = sustain
					
	(second point)
	...
	
	(second envelope)
	...
<----------- end of if flag bit 7

byte		number of levels

(first level)
dword		number of samples
dword		loop begin
dword		loop end
dword		samples per second
byte		root note

(second level)
...

(second wave)
...


=========================================================================

Section 'WAVE' - wave data

Type/Size	Description
-------------------------------------------------------------------------
word		number of waves

(first wave)
word		index of wave	
byte		format:
				0 - raw 16bit, intel byteorder
dword		number of bytes in all levels
  
(data for first level)
..

(data for second level)
...

(second wave)
...

=========================================================================

Section 'BLAH' - song info

Type/Size	Description
-------------------------------------------------------------------------
dword		number of characters
x			raw ascii text (no zero at end)