This is a Jack tool for visual inspection of the signal chain, identification of drops in peak amplitude. For ex. if you suspect the output is low run “meterbridge -t ppm alsa_pcm:playback_1 alsa_pcm:playback_2” and compare it to the output meter in your playback application. In ppm, 1= -12dB, 4 = 0dB, 7 = +12 dB. More Jack meters can be found at Jack Meterbridge.

If this is your problem. You have Rosegarden synced with any other application and are recording with a midi-keyboard. When you play along with the music in the synced app the monitoring is in sync but when you play back the recording the midi-track is out of sync in exact one or more measures. Rosegarden by default comes with a count-in of 2 measures. This can be changed in Settings -> Configure Rosegarden -> General -> Behavior and the parameter “Number of count-in measures when recording”. Set this parameter to 0 and use this settings when recording.

To find out the tempo of an audio recording there's a useful application called BPMdetect. The usage of the application is very straightforward, just add a file or directory and press start. Here's the source-code and a Debian package.