NTSC vs PAL

Friends... thanks for your explainations especially TomH. Now I can surely say that Eropean+middle eastern players of 80s computer games had it easier than those poor Japanese+American counterparts. To me, it is more harder to play Salamander or other fast action games in NTSC speed as it is very hard and speedy as it is in PAL. When I play Penguin Adventure's first stage using openMSX + a Japanese NTSC machine it's like playing the same stage with very high hardness level on my real PAL MSX or using openMSX + Eropean/middle eastern PAL MSX. So NTSC players are more powerful players 'cos their reflexes are more sharp, more speedy than PAL players. Am I right?!

A lot of trackers already have that.

The easiest solution is that the replayer runs at 50hz and when on a 60hz machine it pauzes every 6th frame or something like that.

That's what I'm looking for. A game music replayer for Android & Windoes which allows the user to choose between playing at NTSC tempo or at PAL tempo. I don't think that it would be very hard for the developer of such a replayer to update his replayer in order to implement the support of this feature, isn't it?

What format are the rips in?

Some, such as this .ym, effectively let you dictate the tempo by changing a single value — in that case you should just be able just to change the 16-bit word at offset 26.

It depends on the file format and to what extent your player conforms to the specification, obviously, but one can imagine three classes generally: those where the playback rate is explicit, so you can just change it; those where the playback rate is implicit but the internals are just a list of register values, so you can compress or expand the list; those where the playback rate is implicit and the file is the original executable code that generates the audio, which will be approximately the same amount of work as changing a real game (though hopefully less, as the irrelevant code has hopefully already been edited away, and often those formats are defined as something like call address X every 1/nth of a second, so it's pretty straightforward to determine where an extra counter should be inserted).

I also think that Japanese games were meant to be played at 50Hz and that is more normal. I think games' music composed it at a tempo close to 50Hz than to 60Hz. Otherwise all music would be annoying too speedy to enjoy them. Listen to the music of The Castle on PAL machine with frequent pressing on CTRL & GRAPH keys then compare it on an NTSC machine. Too much speed which takes out the fun of music. So, I think 50Hz tempo was the actual tempo used by composers of Japanese games' music especialky Konami composers.