VTX

Roman Scherbakov (V_Soft) designed this type. This is the best format for storing interrupted music from different AY-3-8910/12 and YM2149 based platforms.

From README.TXT (translation from Russian):

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Offset  Size    Type     Description
00 dec  2 bytes Word     VTX file identifier (ay or ym)
                         Its chip type by default:
                         this is 7961h or 31073 dec (ay)
                         this is 6D79h or 28025 dec (ym)
02      1                Byte bit               Playing mode by default:
                         Bits 0-2 determine stereo mode:
                         0 – MONO, 1 – ABC, 2 – ACB, 3 – BAC,
                         4 – BCA, 5 – CAB, 6 – CBA (dec)
03      2       Word     Loop VBL number (from zero =
                         beginning of melody).
05      4       Dword    AY chip frequency for this melody
                         ( for compatibility with non-Spectrum platforms)
                         Standard values:
                         ZX_Spectrum: 1773400 (or 001B0F58h)
                         Atari: 2000000 (or 001E8480h)
                         Amstrad CPC: 1000000 (or 000F4240h)
09      1       Byte     Player frequency (VBL per sec).
                         Standard value 50 =
                         1/50 sec (20ms).
10      2 bytes Word     Year of composition creating.
12      4       Dword    Size of not packed data.
                         Needed for unpacking.
16      1-255   NTString String with melody name
                         (1-254 chars), must be ended with zero even
                         if no title at all!
??      1-255   NTString String with author name (see ^)
??      1-255   NTString Melody source program (see ^)
??      1-255   NTString Musical editor name (see ^)
??      1-255   NTString Comment string (see ^)
??      ??      Array    Compressed data packet...

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Remarks.

1) Data compressed with LHA type 5. May to pack with LHA.EXE (as YM files), but needed to cut header and last zero byte of compressed file. Header of LHA-archive file is found at start of file. Its length is value of first byte of header plus 2.

2) After unpacking the data block is equivalent to YM3 data block.

Also can be found old version of VTX files (of VTX player older than 2.00 version). AY Emulator can to play it too.

VTX files can be converted from emulators sound dump files (for ZX Spectrum and MSX this is usually PSG-files). But last time you can find emulators, which can to dump music in VTX format too. One of them is Unreal Speccy by SMT.