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‘Mind the Gap, Please!’


The ‘Lydian’ Metamorphosis of the
Classical Harmonic System

Why did Imperial musicians forego the keys that shaped Classical masterpieces such as Euripides’ tragedies or Timotheus’ Persians? And why did rename the traditional, and quintessentially Greek, Dorian mode (Dōristí), and called it Lýdia instead?

‘There are serious puzzles here’,

as Andrew Barker put it many years ago.

A new solution to these, and other, riddles raised by the ‘Lydian’ metamorphosis of Imperial Greek music is offered in my new article in Greek and Roman Musical Studies, which will be available in open access soon.

This article builds upon my previous work on the Classical harmonic system (Lynch 2022a and 2022b), and offers the first account of the historical evolution of the Greek harmonic system and notation keys (tónoi) that bridges the gap between Classical and Imperial music (Figure 1).

The solution presented in the article allows us to reconstruct, for the first time, a continuous, if evolving, tradition that stretches from Euripides’ Orestes to late antiquity, reconciling key theoretical insights provided by Ptolemy, Porphyry and others with documentary evidence that illustrates the structure of the Imperial harmonic system and its use in the Imperial musical documents.

Lynch 2024a, Figure 1: The Lydian metamorphosis of the Imperial harmonic system.

Lynch 2024a, Figure 1: The Lydian metamorphosis of the Imperial harmonic system.
Imperial musicians abandoned the Classical triad of keys–Dorian, Phrygian and Lydian (Lynch 2022a)–and moved to a new system based on the Lydian, Iastian and Aeolian keys

1. ‘Mind the Gap, please!᾽—Ptolemy, Porphyry and the Imperial musical documents

Part 1 of the article shows that Porphyry’s identification of the Hypolydian tónos as the foundational key of the Imperial harmonic system is supported in full by the evidence of the musical documents. 

As shown in Figure 4, 99.1% of the notes attested in Imperial scores do, in fact, fall within the range of the Hypolydian tónos E
2–E4. In keeping with this overarching Hypolydian framework, 84.1% of these notes fall within the Hypolydian central octave B2–B3 and include the diatonic notes that form the conjunct as well as the disjunct tetrachords of this key – i.e. the tetrachords that, by definition, shaped the central octave of the Unchanging Perfect System described in theoretical sources (including the Canon diagram).


The Hypolydian key, therefore, effectively replaced the Classical Dorian as the basic point of reference of the Imperial harmonic system.

Lynch 2024a, Figure 4: The vocal and instrumental notes attested in the Imperial musical documents, and the corresponding structure of the Hypolydian Unchanging Perfect System

Since Classical times, the Hypolydian key corresponded to the basic Lydian tuning called Lydistí (Lynch 2022a). In keeping with the Classical model, the Imperial label Lýdia that is preserved by Ptolemy refers to the same octave range covered by Classical Lydistí (B2–B3), i.e. the central octave of the Imperial system.


As noted by Ptolemy, however, this new central tuning, Lýdia, was shaped in accordance with the Classical Dorian mode. Hence the Classical Dorian mode, centred on mésē F3, turned into the Imperial Lýdia tuning and was notated by the relative notation key, the Hypolydian tónos (mésē E3). Hence Lýdia became the new Dorian (Figure 3). 

Lynch 2024a, Figure 3: The core structure of the Imperial tuning Lýdia: a Dorian octave species (St-T-T-T-St-T-T) set in the Lydistí octave range B2–B3 

Lynch 2024a, Figure 3: The core structure of the Imperial tuning Lýdia: a Dorian octave species (St-T-T-T-St-T-T) set in the Lydistí octave range B2–B3 

In his commentary on Ptolemy’s Harmonics, Porphyry confirms that Ptolemy’s Dorian tuning, Lýdia, was notated by means of the foundational key of the Imperial harmonic system employed in the musical documents, the Hypolydian:

εἰδέναι δεῖ καὶ τοῦτο, ὅτι οἱ κιθαρῳδοὶ τετράσι τόνοις ὡς ἐπὶ τὸ πλεῖστον ἐχρῶντο, τῷ Ὑπολυδίῳ, τῷ Ἰαστίῳ, τῷ Αἰολίῳ καὶ τῷ Ὑπεριαστίῳ.

(Porph. in Ptol. Harm. 156.8–10)   

It is also necessary to understand this, that kitharodes made use of four keys most of the time:
the Hypolydian, the Iastian, the Aeolian and the Hyperiastian.

In keeping with the centrality of the Classical Dorian tónos, Porphyry begins his list with the equivalent central tónos of the Imperial system, the Hypolydian (mésē E3). And just as the Classical modulation system was based on the Dorian, Phrygian, and Lydian keys, Porphyry continues by adding the Imperial counterparts of the other core tónoi: the Iastian key, which Aristoxenus called ‘lower Phrygian’ because it was a semitone lower than the Classical Phrygian key (mésē F#3, a semitone below Phrygian mésē G3); and the Aeolian key, which Aristoxenus called ‘lower Lydian’ for the same reason (mésē G#3, a semitone below Lydian mésē A3).

Porphyry’s list is rounded off by the Hyperiastian key (mésē B3), which Aristoxenus called Higher Mixolydian. Porphyry’s addition of a key related to the Mixolydian mode is not particularly surprising, and follows the historical evolution of the harmonic system outlined by Ptolemy.


Ptolemy had, in fact, described the introduction of the Classical Lower Mixolydian tónos (mésē Bb3) as the ‘first consonant modulation (metabolḗ)’ of the Classical harmonic system, a ground-breaking innovation that was developed by late Classical musicians in order to expand the core modulation system that comprised three basic tónoi (Dorian, Phrygian and Lydian).

Unlike the other keys listed by Porphyry, which are a semitone lower than their Classical counterparts, the Hyperiastian tónos (mésē B3) is a semitone higher than the Classical Lower Mixolydian.


This shift in the relative position of the Mixolydian key had a significant impact on the underlying structure of the Imperial harmonic system. As shown in Figure 6, the Higher Mixolydian tónos is now a fifth higher than the basic key of the Imperial system, the Hypolydian (mésē E3), whereas the Classical Lower Mixolydian (mésē Bb3) was a fourth higher than the central key of the Classical system, the Dorian (mésē F3). 

Lynch 2024a, Figure 6: Classical keys and their Imperial equivalents (Porph. in Ptol. Harm. 156.8–10). The Classical Dorian, Phrygian and Lydian keys are lowered by a semitone, whereas the key that corresponds to the Classical Mixolydian mode is shifted up by a semitone to the Higher Mixolydian/Hyperiastian key

Lynch 2024a, Figure 6: Classical keys and their Imperial equivalents (Porph. in Ptol. Harm. 156.8–10). 

The structural importance of the fifth S E3Z B3 is reflected by is reflected by the Imperial musical documents, where this interval is often used to define the central range of the tunings employed in a given piece – see, for instance, the  beginning of the Seikilos song (Figure 8).

Lynch 2024a, Figure 8: The Seikilos song (DAGM 23)

In the passage quoted above, Porphyry describes the four keys represented in Figure 6 as the tónoi that kitharodes ‘made use of most of the time’ (ὡς ἐπὶ τὸ πλεῖστον ἐχρῶντο), suggesting that other keys could occasionally be used alongside them. The Imperial documents confirm that this was indeed the case, as the Lydian key features prominently alongside the basic Hypolydian/Lýdia tuning.


This alternative setup is described in the Anonyma Bellermanniana, where we read that ‘kitharodes tune their instruments to four keys: Hyperiastian, Lydian, Hypolydian, Iastian’. 

The parallel existence of two alternative arrangements of keys (Figure 9) is less surprising than it may appear from a modern point of view. As Aristoxenus tells us, two alternative systems of trópoi were employed in early Classical times too — a point that has significant implications for the development of the Greek notation system (see Bridging the Gap).

Lynch 2024a, Figure 9: Alternative key arrangements employed in Imperial kithara music (Porph. in Ptol. Harm. 156.8–10; Anon. Bell. §28.8–10)

The alternative arrangement described in the Anonyma Bellermanniana retains the Classical Lydian key in its original position (mésē I A3), while the other keys are identical to the setting described by Porphyry: Classical Dorian and Phrygian are shifted down by a semitone to Hypolydian and Lower Phrygian respectively, and the Classical Lower Mixolydian key is again shifted up by a semitone to the Higher Mixolydian.


Just as in the first setting, this change produced an interval of a fifth between the basic Hypolydian key and the Higher Mixolydian, but this fifth differs from the previous one in its inner arrangement as the minor third is now placed in the middle of the basic fifth S E3Z B3, and not at the top.

Taken jointly, these structural changes undermined the traditional connotations of the Classical harmoníai and produced a new, fundamentally diatonic system rooted in the structural fifth S E3Z B3, which replaced the Classical fourth P F3H Bb3.

As we shall see in a forthcoming book, the interplay of these harmonic settings defined the essence of Imperial Greek tunings and the character of different groupings. For the moment, it suffices to note that the foundational role of the Hypolydian tónos as the Imperial equivalent of the Classical Dorian key—the key that was the fundamental point of reference of the Classical harmonic system (Lynch 2022a)—is uncontested in both settings, in full accordance with the practical evidence of the Imperial musical documents as well as the Canon diagram.

Lynch 2024a, Figure 4
Lynch2024a, Figure 9
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