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Logic: Scale Quantise & MIDI Transposition

Logic Tips & Techniques By Geoff Smith
Published August 2016

Screen 1: You can use the combination of the Chord Trigger and Transposer MIDI effects to create a chord progression in any key.Screen 1: You can use the combination of the Chord Trigger and Transposer MIDI effects to create a chord progression in any key.

Easily play and write in any key with Logic Pro’s MIDI tools.

If you are not a Grade 8 music theory buff or a keyboard player with an encyclopaedic knowledge of scales and chord progressions, then writing music inside a modern DAW can present some challenges when it comes to generating ideas in a specific key or harmonising a chord progression. In this month’s Logic Notes we will look at using Logic’s chord generation and transposition plug-ins to create a backing in a key of your choice. Then we’ll use the MIDI effects in combination with offline randomisation to help you generate melodic ideas. Lastly, I’ll show you a workaround to configure Logic’s Piano Roll to only display the notes within the key you are composing in.

Let’s begin our writing process by recording a chord progression. Create a Software Instrument track and from the Library choose a patch suitable for playing chords. I chose to use Alchemy and the Copenhagen preset. In the channel strip add the Chord Trigger MIDI effect and double-click on it to bring up its editing window. Go to the preset combo box and choose the Songwriter Right Hand preset. Play keys C3 through to C5 on your keyboard to trigger different chords in the key of C major. Now let’s try to write in a different key. Start by adding the Transposer MIDI effect after the Chord Trigger effect. Set the Root field to A# and the Scale field to Natural Minor. Now the Transpose plug-in will force all incoming MIDI notes to the scale of A# minor. Once again, play keys C3 through to C5 until you have found a chord pattern that you like and then record it (see Screen 1 above).

There & Back

One unfortunate limitation of Logic’s MIDI is that in order to edit the MIDI output you have to use a slightly convoluted workaround. Label the existing Software Instrument track Source. To print the MIDI with processing to a new track, duplicate the track and rename it Print, then delete the track’s MIDI effects. Go back to the Source track and replace your Software Instrument with Logic’s External Instrument plugin, then from the MIDI Destination menu choose the name of one of your IAC buses. Logic will now send the MIDI from your Source track through the MIDI effects and out of Logic via the IAC bus. Now, if you record-enable the Print track and hit record, you will hear Logic recording the MIDI from the IAC bus into the Print track. Once you have completed the recording you can delete the Source track.

We now have the full MIDI data for the chord progression, so let’s edit it to make it sound less robotic and more like a real keyboard player. Select the recorded region and go to the Regions Parameters area in the Inspector. Click the disclosure arrow next to ‘More’ to reveal the extended parameters, and then raise the Q-Flam parameter to 151 ticks. The Q-Flam parameter spreads the notes apart — a positive value produces an upwards arpeggio or strum effect while a negative value produces a downwards arpeggio or strum effect. Experimenting with this parameter can help to make your chords sound less mechanical. Another way to achieve a similar result is to add randomisation to the timing and velocity of the notes. Undo your Q-Flam setting and double-click on the region to bring up the Piano Roll. In the Piano Roll editor go to the Functions menu, then MIDI Transform / Humanize. From the pop-up dialogue, click Select and Operate. You will now hear that your chords have many small variations in timing, velocity and length. Experiment with increasing the amount of randomisation by editing the Position, Velocity and Length columns in the Humanize dialogue, until you achieve the desired result.

Melody, Not Malady

Now that we have a backing chord progression in A# minor, let’s move on to create an accompanying melody part in the same key, using a MIDI keyboard. Create a new Software Instrument track and on it choose a lead patch. I used Alchemy’s LoFi 80’s Synth Lead preset. Once again add the Transposer MIDI effect and set it the same as before (Root: A#, Scale: Natural Minor). Now play a random melody on your keyboard and notice how the Transposer MIDI effect auto-adjusts the notes that you play to the scale of A# minor. (Tip: you can even stick to playing the white keys on your keyboard — the Transposer will do the rest!). You should now be able to record a rough melody that works alongside your chord progression. To clean up any overlapping notes you may have unintentionally played, select the offending notes in the Piano Roll and go to Edit / Trim / Note to Remove Overlaps with Adjacent, and from the pop-up choose Shorten.

Screen 2: Randomise the pitches of note events in a region before passing them through the Transposer MIDI effect. This will automatically create variations in your melody part which can be useful for generating new ideas and breaking out of creative ruts.Screen 2: Randomise the pitches of note events in a region before passing them through the Transposer MIDI effect. This will automatically create variations in your melody part which can be useful for generating new ideas and breaking out of creative ruts.

Let’s now experiment with your basic melody by using a different randomisation process to generate some alternatives. Copy the melody parts region and, with the copy selected, open the Piano Roll editor. From the Functions menu go to MIDI Transform / Transposition. Click the drop-down menu in the Pitch column and change the process to ‘+-Rand’ and set the value combo box beneath it to 2. Now click on Select and Operate to listen to your new melody. You should hear that a small amount of random variation has been introduced but that the melody remains in the right key (see Screen 2). Experiment with clicking Select and Operate repeatedly and each time, audition the change in the melody part. For greater amounts of variation you can increase the Random amount from 2 to 5.

I’ve Got The Key

Let’s finish off by looking at how to draw in a melody in our chosen key without inputting wrong notes. Create a new Software Instrument track and pick a preset from the Library suitable for a lead part. One way to draw in notes in the Piano Roll editor and have them conform to our chosen scale is to use the Transposer plug-in as we did previously. However, this is less than ideal as the Piano Roll would still be displayed in a chromatic layout showing us more notes than are in the scale of A# minor, which could make drawing in a simple melody unnecessarily confusing. Although there is no direct way to display just the notes from a specific scale in the Piano Roll editor, there is a simple workaround. On your new track create a new MIDI region and in the Piano Roll draw in a single note for every key on the keyboard ,and then Select All the events (I dragged this Region into my Apple Loops library for quick recall in other projects). Now go to the Inspector on the left-hand side of the Piano Roll and, from the Scale Quantise area, set the root field to A#, the scale to Natural Minor, and press the Q button. Logic now quantises all the note pitches to A# minor. Name this region Template (see Screen 3).

Screen 3: In a new region, draw a note event for every note (left). The Scale Quantize area can then be used to quantise the selected notes to a specific scale; here I have used A# minor (right). Screen 3: In a new region, draw a note event for every note (left). The Scale Quantize area can then be used to quantise the selected notes to a specific scale; here I have used A# minor (right).

In the Arrange page create another blank region and name this Melody. Select both regions, then in the Piano Roll click on the Collapse Mode button next to the View menu. When Collapse Mode is On the Piano Roll displays only the notes that have events, and since we created our Template region to have all the notes in the scale of A# minor, that is what’s displayed. You can now use the Pencil tool to draw notes into the Melody region, safe in the knowledge that they are all in the right key (Screen 4). You can also return to the normal chromatic view by toggling the Collapse Mode button Off.

Screen 4: The Collapse Mode button is highlighted orange next to the View menu item. When engaged, the Piano Roll displays just the notes used — those in A# minor — allowing you to quickly draw in a melody without worrying about inputting wrong notes.Screen 4: The Collapse Mode button is highlighted orange next to the View menu item. When engaged, the Piano Roll displays just the notes used — those in A# minor — allowing you to quickly draw in a melody without worrying about inputting wrong notes.

So there you have it, whether you are a complete beginner or a genius at music theory, Logic has a range of tools to help you create sweet, harmonious music.

Published August 2016

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