The Player is where you'll spend most of your time in the application and it, as you may have guessed, allows you to play the tracks.
The tempo specified by the MIDI file is always displayed below the quarter note symbol in the bottom left and will change as determined by the file. Tapping the quarter note image will display a slider that allows you to adjust the tempo anywhere from 10% to 180% of the actual value. The current real tempo will then be displayed above the quarter note.
This means that for a track that normally plays and 120 bpm, you can have it played back as slowly as 12 beats per minute (excruciatingly slow) or up to 216 bpm if you want to practice at almost double the normal speed.
The tempo adjustment is a percentage value to maximise the effectiveness of your practice session, as changes in tempo within the piece will be realistically reflected even if relatively slowed down.
The tempo adjustment setting will be recorded for every piece, so you can slow down a song you don't know yet and come back to it later without having to reset the tempo every time. When you do want to reset it back to normal, bring the tempo adjustment slider into view by tapping the quarternote symbol, then tap it again.
Adjusting the tempo down is one of the prerequisites to learning a piece right the first time. Another key ingredient is focusing on specific musical segments one at a time, in order to master each one. TrollDrum allows you to focus on any part of the track exclusively, by creating a segment loop.
To create a segment loop, let the track play until the start of the part you are interested in practicing, and press the segment cue mark button. A green drum stick will appear at that point in the track. Wait for the end of the segment, then press it a second time. The end marker (a red drum stick) will appear to mark that position. At this point, the loop segment button will be enabled and pressing it will cause the player to loop between those two points.
It can be difficult to mark the start and end of a loop just right so that the loop will be relatively smooth and you can keep practicing until you get it down. Use the segment cue adjuster to move the start and end marks to precise locations in the piece.
You will hear any percussions events at the current position while adjusting, in order to help you find the right spot.
Each piece will record any segment loop you create, so you can come back to it later without having to reset the cue points every time.
While playing a track, a slider appears at the top of the screen to permit skipping forward and back within the song.
The song loop button allows you to loop the entire song, as opposed to the segment loop button which restricts the loop to the cue points you configured.
The metronome button allows you to toggle quarternote clicks on and off. This is usefull for songs that have "empty" portions in the drum tracks, say during an intro or solo. The click volume is set in Setup.
Three areas of the drum in the interface are marked as shown on the left. Tapping these will emit a snare, kick or hihat sound so you can communicate rythmic ideas directly or tap out a tempo.
The player volume slider is at the bottom of the screen and allows to set the volume anywhere between 0 and the maximum current system volume setting (which may itself be adjusted in the Setup or elsewhere, such as through the iPhone/iPod Music application).
You can select any of the available drum kits on a per-track basis. Each track will store the drum kit you select and use it to play the piece.
To do so, tap the Edit button in the upper right corner of the Player view, or tap the song name, to display the Track Details/Settings.
The details view allows you to see piece-related details as well as set the drum kit and MIDI Channel.
Almost all MIDI files you encounter will have the percussions assigned to the standard drum channel, MIDI channel 10.
However, in instances where you know the file has a drum track but cannot hear them in the player, or get a message to the effect there are no relevant MIDI events, or hear what seems to be some other instrument playing using a jumble of drum sounds, you can try different channels to find the right one.
Head to the Track Details/Settings view, as described above, and select another channel. Try each channel (there are 16 possibilities) until the player plays the drum track.
TrollDrum will remember the last channel you've assigned to the piece, for future play.