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Logic: Editing Chords & Signatures With Global Tracks

Logic Tips & Tricks
By Stephen Bennett

The Global Tracks can not only display chords, key/time signatures, and transpose values — they also let you edit them easily.

In keeping with Logic 's other Global Tracks, the ones dedicated to time signatures and pitch manipulation generally clarify existing Logic functions and make them available in an way that makes them easier to use than they were in earlier versions. As is usual in Logic, the Global Tracks affect either the display of, or the actual data in, other areas of Logic. The Global Tracks covered in this month's Logic article deal with the display and manipulation of transposition (for you budding rock-ballad composers!), chords, time signatures, and key signatures.

Logic: Editing Chords & Signatures With Global Tracks

The Chord Global Track

You may have noticed that when you play a chord on a MIDI keyboard, its name is displayed in the MIDI input/output section of the Transport window — really useful if you want to pass on chordal information to other musicians. If you've recorded a whole sequence of chords, Logic can analyse and display chordal information in the Chord Global Track. To see this in action, play in some chords, make sure the sequence is selected, and then open the Chord Global Track from the View menu. If you then click on Analyse, Logic will display the detected chords on the Global Track. The Change Display Only tickbox will be ticked automatically to prevent your sequences from accidentally being transposed.

You can edit the chord display by double-clicking on its name (if the analysis algorithm has got it wrong) or add chords using the Pencil tool (if it has missed any out). You can also drag and delete chords from the Global Track display using the mouse, Eraser tool, and delete key. But this feature isn't just there to help you pass on your parts to other musicians. The Chord Global Track is closely linked to the Transposition Global Track, and any changes made here can have an affect on the overall pitch of MIDI sequences and Apple Loops.

The Transposition Global Track

If you open up the Transposition Global Track alongside the Chord Global Track, you'll see the effect the different Chords have on the 'root' key of the recording. Just playing back MIDI parts with Change Display ticked will not affect their pitch. However, if you untick it MIDI parts will be transposed accordingly — you can see the amount of pitch change displayed on the Transpose Global Track. Audio-based Apple Loops are always affected by the chord's affect on transposition, even if you have the Change Display Only parameter ticked, so it can cause a bit of confusion when combining the two. Using the Chord Global Track, you can thus easily insert key changes into your Song using basic musical rules, if you like to work this way.

Incoming MIDI data is analysed and its chord type automatically displayed in the Transport window. The Chord Global Track can extract chord information from any selected MIDI sequence in much the same way. If either analysis proves faulty, you can adjust how the detection algorithm responds using the Define Chord window.Incoming MIDI data is analysed and its chord type automatically displayed in the Transport window. The Chord Global Track can extract chord information from any selected MIDI sequence in much the same way. If either analysis proves faulty, you can adjust how the detection algorithm responds using the Define Chord window.Audio files recorded or imported into Logic aren't affected by these transpositions, so if you want to keep everything transposing correctly, you'll need to convert your recording into an Apple Loop first. First select the sequence containing the recorded audio and choose Open in the Apple Loops Utility submenu of the Arrange window's Audio menu — the Apple Loops Utility will start to load and you'll be asked to enter the number of bars you want the Apple Loop to be. It's always best to choose an integer number of bars when you're creating an Apple Loop. In this case, the guitar part is eight bars long. The utility will open and you can choose the key of the recording and some search tags if you want to make the loop easily searchable from the Apple Loop browser. You may also want to add some transient information too if it's a rhythmic recording.

When you're done, click on Save and exit the Apple Loops Utility. Now the guitar recording will follow chord and transposition changes just like any Apple Loop. Note that only Apple Loops which have a Key Definition will be transposed — some, such as the Apple-supplied drum loops, will not. You can use this feature to make sure only the Apple Loops you actually want to change key will be transposed. If you like, removing the Key Definition of any Apple Loop will make your drums to play two octaves lower, trip-hop style.

Of course, you can also edit key changes directly on the Transposition Global Track with the mouse. You can add transposition nodes using the Pencil tool, delete them using the Eraser Tool, and drag them around with the mouse and Arrow tool. If you click on a transposition node while holding down the Control, Alt, and Apple keys, a small text box will open where you can enter the transposition value directly for accurate Whitney Houston impersonations. Setting the transposition value to zero resets the playback to the original pitch. You may notice that changing the value of a node on the Transposition Global Track produces a corresponding change on the Chord Global Track, and vice versa. The 'root' key or zero value of the Transposition Global Track is defined in the Signature Global Track, and the transposition values show the difference between the first key signature value displayed there and the root note of the chord. So if the Key signature is set to 'C', an 'E' chord will produce a transpose value of +4 or -8 (depending if it's transposed up or down), a 'G' will display +7 or -5, and so on.

A Shift Too Far

When using Global Track components that deal with tempo or pitch changes of audio, the key to getting usable results is to keep it simple, because Logic 's pitch- and tempo-matching facilities are not that brilliant (at least up to version 7.2), and you'll only get decent results if you go for minimal changes. Try pitch-changes of a few semitones only, and choose the most suitable algorithm from the Time Machine submenu in the Arrange window's Audio menu — you'll have to use your ears to determine which produces the best results. If you want to go for more exotic pitch changing, you may be better off looking at using some third-party software alongside Logic, such as Celemony Melodyne (which integrates with Logic using Rewire) or Serato's high-quality Pitch 'n Time plug-in. Although the latter is an AU plug-in, it appears in Logic v7.2 or greater as an extra choice in the Time Machine submenu menu. Don't overlook Apple's Tiger-based AUPitch Audio Unit either, as it's capable of some pretty high-quality transpositions. It's exactly the same when dealing with tempo changes too. Try not to apply overly radical tempo changes to audio files, and keep sections small and fixed to the nearest whole beat. Logic can't perform miracles, so sometimes the only solution is to play it again, man...

The Signature Global Track

We've seen that the Signature Global Track is where key signatures can be displayed, added, and edited, but it's also the home of time signatures too. A lot of music these days is resolutely in 4/4 or one of its siblings — albeit with the occasional excursion into triplet territory. But if you're more musically ambitious, or into progressive rock or jazz, you may want to experiment with some more esoteric time signatures. If you've been listening to early Dave Stewart recordings, you may even want to try using multiple combinations of exotic time signatures in the first four bars of a song!

When the Chord and Transposition Global Tracks are linked, Apple Loops and MIDI sequences can be made to follow changes in the chord progression.When the Chord and Transposition Global Tracks are linked, Apple Loops and MIDI sequences can be made to follow changes in the chord progression.If you want to record alongside a click in 7/8 or 11/8, you'll need to set these values at the correct Song Position Line (SPL) position. You can do this by typing time signatures directly into the Transport bar, which will make sure that you'll get a click that will be in the correct time signature for you to play along with. To do this, just move the SPL to the required bar, double-click on the time-signature field in the Transport window and enter the required values. If you do this, you'll see that these values are also displayed in the Signature Global Track. However, if you want to add overdubs to previously recorded audio, or set up a recording session with multiple time-signature changes for you to play along with, you may want to add these directly into their required timeline positions on the Global Track itself using the Pencil tool. Clicking on the Global Track opens a box where you can enter the required values.

It's important to understand that time-signature changes made on the Signature Global Track do not directly affect the playback of any MIDI or audio recordings or Apple Loops — only the click-track playback will be affected. However if you open the Score window you'll see the time signature displayed there too, and you can also add and edit time signatures directly here alongside any key signatures from the Signature Global Track. The Signature Global Track is intimately linked with the Score window, and both will therefore find most use by those who like to edit and print out their dots. 

Published July 2006