Lou Reed · Transformer

Perfect Day

Perfect Day is in B flat major at 146.5 beats per minute.

Tempo

147 BPM · Allegromedian of 298 analyses · 144.6–146.6 across the middle eight tenths

Key: B♭ major2 flats · the key most of the analyses agreed on
Agreement: 88%share of analyses that agreed
Analyses: 298people who ran the extractor
One beat: 409.6milliseconds, 60,000 ÷ BPM
Tuning: 439.5Hz · -2 cents from A 440
Dynamics: 6.49dB the level wanders from its average
Loudness: 0.237Essentia's 0–1 scale, not dB
Danceability: 1.007Essentia's danceability, 0–3

Source: AcousticBrainz, dump of 2022-06-23 (CC0) · MusicBrainz core data, 2026-09-17 (CC0) · how each number is measured. Measured up to 23.06.2022 — AcousticBrainz stopped collecting in 2022, so nothing released after that date is here.

What the numbers say

298 independent analyses of this recording were submitted to AcousticBrainz. Most of them — 88% — put it in B flat major, a key signature of 2 flats. The tempo printed above is the median of the 298 readings; 90% of them land within 2% of it, and the middle eight tenths of them run from 144.6 to 146.6 BPM.

At 146.5 BPM one beat lasts 409.6 milliseconds, so a sixteenth note is 102.4 ms and a dotted eighth 307.2 ms — the delay times for this recording. Counted half as fast it is 73.3 BPM, counted twice as fast 293. A score would mark that Allegro, by the ranges this site uses.

The analyses put the reference pitch of the recording at 439.5 Hz, which is 2 cents below concert A at 440 Hz — close enough to standard that a tuner would not argue. That is a fact about this transfer of the music, not about how it was played.

The dynamic complexity of the recording measures 6.49 dB: that is how far the level wanders from its own average, so a small number means a loud, flat master and a large one means a recording that still breathes. Its average loudness is 0.237 on Essentia's 0-to-1 scale, which is not decibels and is not comparable to a streaming service's number.

10 other recordings here are in B flat major; the ones listed below are the closest in tempo.

Beats per bar are not in this dataset. AcousticBrainz's analysis reports a tempo, a key and a loudness, and no time signature at all, so this page does not print one — a 4/4 here would be a guess dressed as a measurement.

Keys that fit with B♭ major

Each of these differs from B♭ major by at most one accidental, or shares its tonic. That is the whole of what a mixing wheel encodes; here the relations are named instead of numbered.

Delay times at 147 BPM

Note value	Beats	Milliseconds	Hertz
Whole note	4	1638.2	0.61
Half note	2	819.1	1.22
Dotted quarter	1.5	614.3	1.63
Quarter note (one beat)	1	409.6	2.44
Quarter triplet	0.667	273	3.66
Dotted eighth	0.75	307.2	3.26
Eighth note	0.5	204.8	4.88
Eighth triplet	0.333	136.5	7.33
Dotted sixteenth	0.375	153.6	6.51
Sixteenth note	0.25	102.4	9.77
Sixteenth triplet	0.167	68.3	14.65
Thirty-second note	0.125	51.2	19.53

Half time 73.3 BPM · double time 293 BPM. Every row is one beat (409.6 ms) times the fraction in the second column.

Closest in key and tempo

Recordings in B flat major, ordered by how near their tempo is to 147 BPM. A calculation, not a recommendation.

All songs in B flat major All songs at 147 BPM B♭ major at 140–149 BPM

MusicBrainz collapses 31 recording ids into this one. Recording id 56856396-51ec-4e14-903a-3ef478bac052.