Changing BPM

How to change BPM value of the existing song?

Usually you should not have any reason to change the BPM of the existing song - you are supposed to set the correct value before you even start vocal track transcription.

Changing the value later may break your synchronization - the start and end positions of all notes will have to be reviewed once again.

In order to avoid the necessity of fixing BPM, use software like MixMeister BPM Analyzer for determining the correct BPM value before you start working on vocal transcription. Remember to multiply the given value by 2 until it falls in the advised range of 200-400 (for fast song 250-500 may be better).

Why changing the BPM value is risky?

As you probably already know, positions of notes in Ultrastar format are expressed in beats and the duration of the beat in milliseconds depends on the BPM value.

For example if you have a note that begins in beat 10 with BPM 240 (so one beat lasts 250 ms) it means that the note begins at 2.5 second (let's assume GAP is 0). If you just change the BPM value to 120 (so one beat will now last 500 ms), your note will now start at 5th second of the audio!

If you make small corrections, e.g. change 240 to 240.05, the synchronization will probably still be fine. However, the bigger the change and the further away the note is from the start of the song - the more its synchronization will be ruined.

Rescaling to new BPM value

Instead of just changing the value, you can use rescale option. Rescaling will not only change the BPM but it will also recalculate the start beats and lengths of all notes in an attempt to preserve the absolute positions and durations in milliseconds as well as possible.

Rescaling is not 100% exact!

Beats can only be expressed as whole numbers. Therefore rescaling will almost always require rounding and will introduce some small differences in absolute positions or durations in milliseconds.

Multiplying BPM by 2

If the BPM value you have chosen is generally correct, but you have just realized that you need more granurality, the best idea is to rescale the song to the duplicated BPM value. This operation is 100% safe and will preserve your synchronization since all positions and lengths in beats will just be duplicated.

To multiply the BPM value by 2 you can either:

use ctrl + M shortcut
go to menu Tags -> BPM -> Multiply by 2
go to menu Tags -> BPM -> Edit...

You should see a popup with current BPM value:

Click the button with >> sign to duplicate the BPM value:

Now choose the Rescale option to rescale the song to new value.

Dividing BPM by 2

If you want to decrease the granularity of your song, you can rescale the song to the BPM value divided by 2. Please note that this operation is not 100% exact - all numbers in beats will have to get divided by 2 so if e.g. the duration of some note was previously 5 beats, now it will be rounded to 2 beats (2.5 is not allowed).

To divide the BPM value by 2 you can either: