INTRA-MEASURE TEMPO CHANGES FOR SEQUENCER PLUS MK II Sequences created using Seq+'s edit function may have a "mechanical" or "player piano" feeling due to the precise execution of MIDI's note-on command on the beat. The lack of "feel" is evident when the composed song is compared with a version recorded by a skilled performer, especially with jazz and blues tunes. Roland has recognized the "feel" problem in rhythm tracks with its introduction of the R-8 drum machine. Randomization of start times (and often durations) is one approach to loosening up jazz and blues tunes. Randomization, however, requires a good bit of repetitive experimentation and just plain patience. A few of the jazz sequences available on the IEMUG BBS include a rapidly- changing tempo track which varies the tempo WITHIN the measure. In most (or all) cases, the tempo is adjusted about 5% or so from the mean. I have seen no documentation explaining how to create this effect, either in the Seq+ Mk II manual or articles I've seen on using Seq+. Dave Phillips refers to the technique in his pending article, POWERSEQ.ARC, available on the IEMUG BBS, and has used it in several sequences uploaded to the BBS. A full explanation of the method used to create the effect was not included in the draft. After some experimentation, I was able to duplicate the technique. This monograph (?) documents a method to create various types of repetitive intra-measure tempo changes (IMTC) with Seq+. The numerical relationships between tempo changes and delay in clicks, as well as sample sequences demonstrating IMTC are included. THE THEORY OF IMTC IMTC, in its simplest form, can be thought of as frequency-modulation of the tempo with a triangular waveform: BPM +5% Tempo 84 - 5- - 83 - - 4- -6 - - 82 - - 3- -7 - - 81 - - 2- -8 - - Nominal 80 - ----- - -----1- ----- -9----- - ------ - ----- - 79 - - 10- -16 - - 78 - - 11- -15 - - 77 - - 12- -14 - - -5% Tempo 76 - 13- - Beat (Case 1) 1 2 3 4 1 2 3 Beat (Case 2) 1 2 3 4 1 2 3 4 1 2 3 4 1 In the above case, 16 uniform tempo changes occur per modulation cycle (MOD 16). If the time signature of the song is 4/4, and the meter of the tempo track is 1/16, the tempo changes will be "in phase" with the song and thus repetitive from measure to measure (Case 1 above, IMTC1TRI.SNG). The same will be true for 1/8 (Case 2, IMTC2TRI.SNG), 1/4 and 1/2 tempo track time signatures for song time signatures with numerators 2, 4, 8, 16, etc. The pattern will repeat every two measures for 1/8, every four for 1/4 and eight for 1/2 tempo tracks (synchronous IMTC). The two examples above are exaggerated (50% modulation) for demonstration purposes. If 3/4, 6/8 or 12/8 song meter is used, 12 or 24 tempo changes per cycle would be selected when synchronization is desired. If you are writing in 2/2 or 2/4 time, you are limited 8 tempo changes per cycle for single-bar synchronization because Seq+ will not accept 1/32 as a time signature. Obviously, one may use other patterns (sawtooth, trapezoid, square) to create a desired effect. Swing effects, an option built into some synths and drum machines, delay the third beat by a specific number of clicks. This can be simulated with IMTC by slowing the tempo of the second beat and speeding up the third by an equal amount. The modulation, in this case, is a rectangular wave. To calculate tempos for a swing effect, assuming n/4 master tempo and a desired delay in clicks: Ts = Tn*(Rc - Dc)/Rc Tt = Tn*(Rc + Dc)/Rc where Rc = Resolution, clicks/quarter-note (ppqn) Tn = Nominal tempo, beats/minute (bpm) Ts = Second beat tempo, bpm Tt = Third beat tempo, bpm Dc = Third beat delay, clicks thus, if the resolution, Rc, = 192 ppqn, the nominal tempo, Tn, = 120 bpm, and the third beat delay is 6 clicks, the second beat tempo = 120*(192 - 6)/192 or 116.25 (116) and the third beat tempo = 120*(192 + 6)/192 or 123.75 (124). Since only a resolution of four tempo changes/bar is required, a 1/4 tempo track with entries 120, 116, 124 and 120 can be used. A 120, 117, 125, 120 pattern can be used to accentuate the effect. There is, of course, no fixed requirement that beat 4 return to the nominal tempo. A portion of Scott Joplin's The Entertainer, in 2/4, is used as an example (IMTC3ENT.SNG) because of its consistent rhythmic pattern. The tempo track is in 1/8 with four entries, 75, 72, 78, 75 followed by the loop. In this case, the second 1/8-note of beat one is lengthened and the first 1/8-note of beat two is shortened: Dc = Rc - Rc*(Tn/Ts) = Rc*(1 - Tn/Ts) thus, for The Entertainer, Dc = 192*(1 - 72/75) = 8 clicks delay. By using a tempo track of higher resolution, the fourth 16th-note of the first beat can be delayed and the first 16th-note of the second beat shortened. The tempo track is in 1/16 and the entries are 75, 75, 75, 72, 78, 75, 75, 75 (IMTC4ENT.SNG). The differences between the two Joplin sequences are subtle, but careful listening can distinguish them. Edit the tempo tracks in the two files, increasing the delay (try 65 and 85), to accentuate the difference between them. IMTC5RAG.SNG, 32 bars of Dave Brubeck's It's a Raggy Waltz, is an example of a synchronous delay in 3/4 meter with a nominal tempo of 155 bpm. The last 1/8-note of the first beat is extended (150) and the second and third beats ramped from 160 down to 153. See appendix for drum note assignments of the Yamaha RX-17 drum machine used in this sequence. Synchronous IMTC can be combined with other effects to alter the feel of the music. Track offsets (try half the number of delay clicks to start) give interesting results, especially with blues tunes. Synchronous IMTC can be used in combination with start-time randomization - less randomization is usually required to obtain the desired feeling. Multi-bar synchronization, where the delays change from bar to bar may also be useful. As noted above, select the a track resolution (meter) which will give the desired number of bars in the cycle. ASYNCHRONOUS IMTC An effect similar to start-time randomization can be created by using a tempo track length which is not evenly divisble by the number of beats per measure. This is the technique mentioned by Dave Phillips in his pending article. Usually, the highest resolution tempo track (1/16) is best for this approach. The longer the track, the better, and prime-number track lengths seem to be best to minimize audibility of the loop. Tempo variations of +/- 3 to 5% of the nominal bpm is the place to start. IMTC6RAG.SNG, Brubeck's Raggy Waltz is an example of the use of async IMTC. A saw-tooth modulating waveform will often give interesting (strange?) results: BPM +5% Tempo 84 -2 - - - - - 83 -3 - - - - - 82 -4 - - - - - 81 -5 - - - - Nominal 80 ------6------------------------------------------ 79 -7 - - - - 78 -8 - - - - 77 -9 - - - - -5% Tempo 76 -1 - - - - - Beat 1 2 3 4 1 2 3 4 1 2 3 4 1 Ansynchronous IMTC is, of course, pseudo-random. It may be effectively use to minimize randomization to an "optimum" feeling. Three examples of its use in blues tunes for piano are available on the IEMUG BBS as PIANOBLZ.ARC. CREATING AN IMTC TRACK WITH SEQUENCER PLUS MARK 2 The following procedure is used to create an IMTC tempo track with Seq+ Mk 2 Ver. 2.1. It is presumably operable with Mk 1 and Mk 3, but has not been tested with them. The following steps are all within View mode: 1. Create a one bar track of the desired tempo track time signature (1/2, 1/4, 1/8, 1/16) using the Add function to allow independent selection of the time signature of the measure. 2. Set the time signature options to Fixed Track and select the number of the tempo track you just created. Set the Default time signature to that of your tempo track (1/2, 1/4, etc.). 3. Select Tempo function and enter the desired numerical tempo values. Make sure that the time signature shown in the tempo track window corresponds to that selected. If not, check your time signature and fixed track number Option settings above: 旼컴컴컴컴컴컴컴훂EMPO TRACK컴컴컴컴컴컴컴커 � ��������L頰頰頰沆頰頰頰沆頰頰頰沆頰頰頰� � ON Tempo 75 Bar 1 (1/16) � 읕컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴컴켸 4. Enter a Loop at the end of the tempo change track. If you are creating a new tempo track after having Removed one, Seq+ appears to automatically insert a Loop at the last position of the IMTC track. 5. Select Options and change the number of the fixed track to your master tempo track or to a track of your choice and set default time signature back to its original value. 6. You may then delete the added IMTC note (not tempo) track, if desired. CAVEAT It should be noted that the use of IMTC precludes use of the tempo track for overall accel/ritard functions because it is used in single-measure looped mode. If multiple tempos are used, and particularly if odd meters (5/4, 9/8, etc.) are inserted, it is best to use a separate track for any measures with different time signatures, adding corresponding blank measures of the default meter to the master track controlling the tempo. Otherwise you may find the bar and tempo track sync off by one or more beats after executing the odd meter bar(s). I've often found it necessary to do this with Seq+, even without IMTC (e.g., when sequencing Charles Ives' works). FROM THE AUTHOR If you have any comments on or corrections to the above, or suggestions which may expand the effectiveness of IMTC with Seq+, please drop me a note or leave a message on the IEMUG BBS. Roger Jennings 1030 Clarendon Crescent Oakland, CA 94610 415-839-9422 APPENDIX: DEFAULT SETTINGS OF RX-17 RHYTHM PROGRAMMER Name Notes Midi Name Notes Midi Name Notes Midi Agogo H D#6 75 Bass Drum A 3 45 Bass Drum A 3 45 Agogo L D 6 74 Tom 3 C 4 48 HH Closed A 4 57 Bass Drum A 3 45 Tom 2 D 4 50 Timbale L A 5 69 Bongo H G#5 68 Rim Shot D#4 51 Timbale H A#5 70 Bongo L G 5 67 Snare Drum E 4 52 HH Open B 4 59 Claps F#4 54 Tom 1 F 4 53 Tambourine B 5 67 Conga HMT F#5 66 Claps F#4 54 Tom 3 C 4 48 Conga L E 5 64 Cowbell G 4 55 Crash C 5 60 Cowbell G 4 55 Shaker G#4 56 Tom 2 D 4 50 Crash C 5 60 HH Closed A 4 57 Ride D 5 62 Cuica H F 6 77 HH Open B 4 59 Agogo L D 6 74 Cuica L E 6 76 Crash C 5 60 Rim Shot D#4 51 HH Closed A 4 57 Ride D 5 62 Agogo H D#6 75 HH Open B 4 59 Conga L E 5 64 Snare Drum E 4 52 Ride D 5 62 Conga HMT F#5 66 Conga L E 5 64 Rim Shot D#4 51 Bongo L G 5 67 Cuica L E 6 76 Shaker G#4 56 Bongo H G#5 68 Tom 1 F 4 53 Snare Drum E 4 52 Timbale L A 5 69 Cuica H F 6 77 Tambourine B 5 78 Timbale H A#5 70 Claps F#4 54 Timbale H A#5 70 Agogo L D 6 74 Conga HMT F#5 66 Timbale L A 5 69 Agogo H D#6 75 Whistle F#6 78 Tom 1 F 4 53 Cuica L E 6 76 Cowbell G 4 55 Tom 2 D 4 50 Cuica H F 6 77 Bongo L G 5 67 Tom 3 C 4 48 Tambourine B 5 78 Shaker G#4 56 Whistle F#6 78 Whistle F#6 78 Bongo H G#5 68 -30-