Jester <> wrote: Samples are of crucial importance in mods. Good samples make the difference between a quite-good and a great mod. And since custom samples are one of mods' greatest advantages, a lot of attention should be paid to a wise choice in samples.

It is important to know the main two qualities a sample has, the resolution, i.e. number of bits, and its sampling rate. The number of bits in a sample denote its ability to distinguish between levels of amplitude, a higher number of bits can grasp a sound more accurately than a low one. The sampling rate is directly related to the highest frequency that can be reproduced by the sample. A sample with a sampling rate of 40kHz, for example (kHz means 1000Hz, 1Hz is one oscillation per second), can reproduce sounds of up to 20kHz. This means that low sampling rates can be used to reproduce low sounds, but reproduction of high frequencies (cymbals, but also pianos) require higher sampling rates. The theory behind this is known as the Nyquist theorem.

Another aspect of mods is the maximum size a sample is allowed to have. This varies in the file formats from 64 Kilobytes to virtually unlimited size. Note that some trackers impose harsher limits on sample length than the formats they output. The solution offered to the sample size problem is sample looping. Well placed loop points make quite a difference in sustained instruments, so spend enough time here.

Sample formats seem to be a very confusing subject in the mod community. Especially SAM and SMP don't seem to be at all well understood. Keep in mind that filename extensions can be arbitrarily chosen and changed in most operating systems, so they lose any identifier quality. Thus I consider sample formats those files which can be identified by some sort of header. SAM and SMP, when meaning MOD (i.e. M.K., xCHN, FLTx, NST, etc.) samples, do not have any header. They are simply data assembled in a file. A tracker using them decodes them to 8-bit raw signed sample data. But it assumes a playback rate to be used. Normally, finetune and loop values can not be stored in MOD samples (Fasttracker 1 circumvents this problem by abusing the file's date and time stamp). The only safe method to exchange MOD samples is to use these in MOD files and exchange these (if there are other safe ways on the Amiga or another platform, please correct me). See section 5.1.3 on how to convert to "SAM format".

Additional information can be found (and is strongly recommended) in:

The Audio File Formats FAQ by Guido van Rossum <>, posted to alt.binaries.sounds.{misc,d} and comp.dsp once a fortnight, and available in distributed hypertext form as

Also, if you do any decent web search you'll come up with lots of links. I found this, a good site for more specialised (ie MOD) formats:

The The Cross-Platform Page: Audio Formats at:

is a very useful information site if you want to extend the file formats into such areas as Real Audio and MP3 Compression.

Hugh Hulme <> also added: Wotsit's collection of File Formats, which includes EVERYTHING on EARTH is at..

At first I thought Hugh was kidding but this site really does have EVERYTHING you ever needed to know about the innards of this machine we all spend so much time with...

PATREF24.ZIP - Windows Help file describing how to convert a variety of samples to GUS-usable patches. Most of the information supplied is very handy in any type of instrument sample conversion. 2PAT is also supplied, a Windows sample conversion utility (great!). This file is available at the GUS sites, see section 6.1.


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