GitHub Chris Webb

Yamaha Montage ≫ Top-level file structure

Montage X7U, X7L and X7A files all have an identical structure, but dump different subsets of the internal storage. In particular, to load an X7L file into the user bank, just rename the file with an X7U extension. Similarly, to load an X7U file into a library slot, just rename it with an X7L extension.

MODX X8U, X8L and X8A files also have the structure described in this document, apart from the different extension and file version in the header. The detailed content of some of the data blocks may differ, however.

Unless otherwise specified, in what follows all indices are zero-based, all sizes, lengths and offsets are bytes, and integers are in big-endian order. Montage lacks an RTC, so to allow lists to be date-sorted, it uses an arbitrary 32-bit incrementing counter as a proxy for time stamps.

The “Full Tines 2” preset may be useful if the eccentric, ad-hoc design of these binary files induces unexpected 1980s flashbacks.

The file header looks like:

0x00  59 41 4d 41 48 41 2d 59  53 46 43 00 00 00 00 00  |YAMAHA-YSFC.....|
0x10  34 2e 30 2e 35 00 00 00  00 00 00 00 00 00 00 00  |4.0.5...........|
0x20  nn nn nn nn ff ff ff ff  ff ff ff ff ff ff ff ff  |................|
0x30  ll ll ll ll ff ff ff ff  ff ff ff ff tt tt tt tt  |................|

File version “4.0.5” is current for Montage firmware v3.00 to v3.51. File version “5.0.1” is used by MODX firmware v2.00 to v2.52.

n is the size of the catalogue which follows the header, l is the size of the library info immediately after the catalogue, and t - 1 is the most recent time stamp on an item in the file.


Top-level blocks of data within these files are identified by four letter chunk IDs, for instance “EPFM” or “DPFM”. The catalogue consists of eight byte entries, each being the four byte identifier followed by the 32-bit offset of that block within the file.

Here is an example catalogue from an empty X7L file:

0x40  45 50 46 4d 00 00 00 f1  44 50 46 4d 00 00 00 fd  |EPFM....DPFM....|
0x50  45 57 46 4d 00 00 01 09  44 57 46 4d 00 00 01 15  |EWFM....DWFM....|
0x60  45 57 49 4d 00 00 01 21  44 57 49 4d 00 00 01 2d  |EWIM...!DWIM...-|
0x70  45 41 52 50 00 00 01 39  44 41 52 50 00 00 01 45  |EARP...9DARP...E|
0x80  45 43 52 56 00 00 01 51  44 43 52 56 00 00 01 5d  |ECRV...QDCRV...]|
0x90  45 4c 53 54 00 00 01 69  44 4c 53 54 00 00 01 75  |ELST...iDLST...u|

Library info

Following the catalogue and before the first block, there is an area with a source filename and other info for each of the populated library slots. In the simple case where all library slots are empty, it consists of 80 0xff bytes followed by a single 0x00 byte, this length of 81 being declared in the file header:

0xa0  ff ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  |................|
0xb0  ff ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  |................|
0xc0  ff ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  |................|
0xd0  ff ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  |................|
0xe0  ff ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  |................|
0xf0  00                                                |.|

A self-contained X7U or X7L won’t refer to waveforms, arpeggios or curves from other libraries, so the library info can be left empty like this for such files.

However, more generally an X7A or X7U file records info for every library installed on the instrument when it was saved. The initial 80 bytes comprise eight chunks of 10 bytes, one for each library slot. If a slot is occupied, the chunk will be 00 ii 01 ii 02 ii 03 ii 04 ii where i ranges from 0x02 to 0x09 for slots 1 to 8. Otherwise there are just 10 0xff bytes.

Following this, there is a single byte count n of occupied slots(0x00 to 0x08) followed by n variable-length descriptions of each occupied slot with the following format:

The sizes of waveform and non-waveform data are used in the Utility -> Contents -> Data Utility display, but the exact rule to calculate these from the file contents is not yet documented here.


After the catalogue and padding, the blocks listed in the catalogue follow one by one until the end of the file. Each block has the following format:

There are two types of blocks, present in matching pairs. An entry list has type beginning with ‘E’, e.g. “EPFM”, and its corresponding data block has a type beginning with ‘D’, e.g. “DPFM”. The ‘E’ block should preceed the ‘D’ block in the file; order doesn’t seem to matter otherwise.

Entry lists (“Exxx”)

Following the 12-byte block header, an entry list concatenates zero or more entries of the form:

The number of entries must match the count described in the entry list header and the number of items in the corresponding data block.

Program numbers generally have a bank number (0x0001 = User, 0x0002 = Library 1, 0x0003 = Library 2, …, 0x0009 = Library 8) in the most-significant 16-bits, followed by a zero-indexed item number in the least-significant 16-bits. Some exceptions to this are described below.

Data blocks (“Dxxx”)

Following the 12-byte block header, a data block concatenates zero or more item chunks of the form:

The number of items must match the count described in the block header, and n must match the item size stored in the entry list for this item.

Block types

Listed in the order used by the instrument, which first saves all non-empty entry lists “Exxx”, then the data blocks “Dxxx”:

Performances (“EPFM”)

Performances are numbered to match their MIDI number: 0x00xxyyzz corresponds to bank MSB x, bank LSB y and program z. Note this means x, y and z range from 0x00 to 0x7f, not 0xff. For reference, the following ranges are used:

The 6-bytes of flags in the entries are allocated as follows:

The arpeggiator flag is enabled if both the master switch and at least one part switch is on. The motion sequencer flag is enabled if the master switch is on and either the superknob lane is active, or the common sequence is active with active lanes, or at least one part sequence is active with active lanes.

One or more bits are set in the category bitmask corresponding to the categories of parts contained in the performance: 0x0001 = Piano, 0x0002 = Keyboard, 0x0004 = Organ, etc.

The zero-terminated name string contains the numeric category and subcategory of the first part followed by a ‘:’ and the name of that part, for example “66:FM Hybrid Bass”. This is identical to the category:name string in the performance data for that part.

The zero-terminated title string contains the unprefixed name of the performance itself, for example “FM Hybrid Bass”. Both this name and the part names are sometimes padded to a length of 20 bytes with space characters 0x20, but the instrument itself doesn’t do this.

These are followed by zero or more 32-bit program numbers of non-preset waveforms used by the performance.

Waveforms (“EWFM” and “EWIM”)

The are two types of entry list for waveforms. “EWFM” and “DWFM” blocks contain the (small) waveform metadata, whereas “EWIM” and “DWIM” blocks contain the corresponding (large) wave data itself.

Waveform program numbers have the usual bank number in the most-significant 16-bits, and a number between 0x0001 and 0x0400 in the least significant 16-bits. Waveform 0x0000 is reserved for empty elements, so for example the first and second user waveforms are 0x00010001 and 0x00010002.

The six flag bytes are apparently unused apart from byte 3 which contains the favourite flag: 0x00 = unset, 0x01 = set.

The zero-terminated name string contains the numeric category and subcategory followed by a ‘:’ and the waveform name, for example “66:Analog Bass1”.

System settings (“ESYS”)

This list has a single entry numbered 0x00000000 and named “System”, containing all the settings.

Favourites (“EFVT”)

The favourite flag in the entry lists is only used to mark favourite performances, arpeggios and waveforms for user banks. The flags in the library info area are used to record favourite choices for libraries.

However, users also also need to be able to mark preset items as favourites without modifying the original so there is yet another ad-hoc mechanism for this. “EFVT” and “DFVT” blocks have one entry for each list type, named “PerformanceFavorite”, “ArpeggioFavorite” and “WaveformFavorite” respectively. The data for these is a block of flag bytes (0x00 = unset, 0x01 = set), one for each preset of that type.

Patterns, pattern chains and songs (“EPAT”, “EPCH” and “ESNG”)

Songs and patterns are stored globally, not in user or library banks. As a result, they are only exported in X7A backup files, not X7U user files, which often catches out users. However, they are numbered as though they live in the user bank: 0x00010000, 0x00010001, etc.

Contact and credits

Please send any questions, corrections or other contributions to Chris Webb <>.

The library info area was documented in collaboration with Derek Cook of x.factory Librarians following discussions on GitHub, and he also provided the precise definition of the performance arpeggiator and motion sequencer attribute bits. Derek has delved into the content of data blocks (such as performances and smart morph maps), posting a lot of useful research beyond the basic structure documented here.