diff --git a/Semantics.Music/Chord.cs b/Semantics.Music/Chord.cs
index 3c7e49d..274be80 100644
--- a/Semantics.Music/Chord.cs
+++ b/Semantics.Music/Chord.cs
@@ -367,7 +367,10 @@ private static bool IsMinor(string body) =>
 	private static SeventhType DetermineSeventh(string body, ChordQuality quality)
 	{
 		bool hasSeven = body.Contains('7');
-		bool hasMaj7 = body.Contains("maj", StringComparison.Ordinal) || body.Contains("M7", StringComparison.Ordinal) || body.Contains('Δ');
+		bool hasMaj7 = body.Contains("maj", StringComparison.Ordinal)
+			|| body.Contains("Maj", StringComparison.Ordinal)
+			|| body.Contains("M7", StringComparison.Ordinal)
+			|| body.Contains('Δ');
 
 		// The major seventh is tested first because one body can carry both spellings: "dimmaj7"
 		// is the diminished-major seventh, a chord distinct from "dim7", and it is what the
@@ -379,7 +382,9 @@ private static SeventhType DetermineSeventh(string body, ChordQuality quality)
 			return SeventhType.Major;
 		}
 
-		if (quality == ChordQuality.Diminished && body.Contains("dim", StringComparison.Ordinal) && hasSeven)
+		// '°' is accepted here as it is for the triad, so "C°7" is the diminished seventh rather than
+		// falling through to a dominant seventh on a diminished triad, which is the half-diminished chord.
+		if (quality == ChordQuality.Diminished && (body.Contains("dim", StringComparison.Ordinal) || body.Contains('°')) && hasSeven)
 		{
 			return SeventhType.Diminished;
 		}
diff --git a/Semantics.Test/Music/ChordTests.cs b/Semantics.Test/Music/ChordTests.cs
index f7d142f..b243300 100644
--- a/Semantics.Test/Music/ChordTests.cs
+++ b/Semantics.Test/Music/ChordTests.cs
@@ -69,6 +69,20 @@ public void ChordTones_DiminishedMajorSeventh_HasTheMajorSeventhNotTheDoubleFlat
 		Assert.AreSequenceEqual([0, 3, 6, 11], actual, "Cdimmaj7 should be a diminished triad with a major seventh.");
 	}
 
+	[TestMethod]
+	[DataRow("CmMaj7", ChordQuality.Minor, SeventhType.Major, new[] { 0, 3, 7, 11 })]
+	[DataRow("CMaj7", ChordQuality.Major, SeventhType.Major, new[] { 0, 4, 7, 11 })]
+	[DataRow("C°7", ChordQuality.Diminished, SeventhType.Diminished, new[] { 0, 3, 6, 9 })]
+	public void Parse_AlternativeSeventhSpellings_GiveTheSeventhTheyName(string symbol, ChordQuality quality, SeventhType seventh, int[] tones)
+	{
+		// A round-trip alone cannot catch these: the misparsed chord formats and re-parses
+		// consistently, so the seventh type and the pitches have to be asserted directly.
+		Chord c = Chord.Parse(symbol);
+		Assert.AreEqual(quality, c.Quality, symbol);
+		Assert.AreEqual(seventh, c.Seventh, symbol);
+		Assert.AreSequenceEqual(tones, [.. c.ChordTones()], symbol);
+	}
+
 	[TestMethod]
 	public void Parse_HalfDiminished_IsDiminishedTriadWithDominantSeventh()
 	{