RH Wiki:BPM
This policy provides information regarding listing a game's BPM in its infobox.
What is BPM?
A song's tempo is essentially how fast the song plays, measured in beats per minute. In the Rhythm Heaven Series, every game naturally needs a tempo to dictate how fast it plays, both the music and the gameplay accompanying it. This is not something the games ever explicitly show to the player, instead letting them get into the groove on their own. Rhythm Heaven Wiki has long had difficulty in finding how to best convey this information, and decided not to show it at all for a while. Nowadays, BPM returned to the pages, albeit in an imperfect manner; Below are the few imperfections you may need to be wary about while consulting BPMs on the wiki.
Refresh Rates
Due to the refresh rate of the Game Boy Advance and Nintendo DS families of systems not being an exact 60 FPS, the tempo for sequenced music in games played on these systems is effectively slower than what the internal value suggests it should be. For example, a game in Rhythm Tengoku set to 120 BPM internally would actually play closer to 119,455001139212 BPM on original hardware due to this. This discrepancy would mean the objective, internal value would be inaccurate to what actually happens during gameplay, and as Rhythm Tengoku can be played on multiple models and consoles, through emulators, and an arcade port, each with their own differences in refresh rates, what the exact effective tempo would be can vary quite a bit. The same holds true for sequenced music in later games to potentially lesser extents.
Streamed music does not provide a completely objective number either, due to being stored as the duration of the song in beats and duration in seconds divided by the sample rate. This creates tiny inaccuracies in tempo, for example Karate Man Combos! is set to 402 beats and 4 287 988/32 000=133,999625 seconds. Diving the beats by the seconds and multiplying by 60 FPS, we get 180,000503732753 BPM. This can be reasonably rounded to 180 BPM, with the decimal difference being negligible, though the exact decimal can also be unclear.
Internal values, subjective BPMs, and external sources
Some games may "feel" as a different tempo to what the game considers it to be. For example, Rap Men is, disregarding refresh rates, internally 180 BPM, but "feels" like 90 BPM during gameplay. This has led to disagreements over whether the number should be the more objective internal value, or the more subjective one.
Internal Values
For the standard BPM section, it has been decided that the closest objective value (that is, the internal value of the song) would be used. It is the closest we can get to an "official" BPM value for the song and as such, is the only accurate value we can display.
Speedups in songs
Some songs include speedups in the middle. While some might be extracted from the game (such as when it is located in a tempo table), some others might use the game's speedup commands and need to be calculated. This might result in imperfect tempos.
CD BPMs
For the CD BPMs, the value show might be inaccurate, as there is no internal value, or official statement regarding the speed at which is plays. In the case of songs such as Rap Men or Love Lizards where the "felt" tempo is half speed, the value will still be chosen as to be closest to the internal values, being 180BPM and 204BPM respectively, as those are the closest to official we can get.