Time Stretch and Pitch Shift in Sound Forge

Quick answer: use Process → Time → Time Stretch or élastique Timestretch when duration must change but pitch must stay fixed. Use Effects → Pitch → Shift when pitch must change but duration must stay fixed. Use Effects → Pitch → Bend for a pitch change that moves over time; keep Preserve original duration on only when the file length must remain fixed. For a constant tape-speed or turntable-speed correction, use Process → Resample with Set the sample rate only, because that intentionally changes playback rate, duration and pitch together.

Decide what must stay unchanged before opening a process. “Make it faster” could mean shortening narration without a chipmunk voice, matching a loop to a new BPM, tuning a flat note without moving an edit point, or correcting a record transferred at the wrong speed. Those are four different jobs. The right menu path matters, but the target calculation and the rejection test matter more.

Time Stretch vs Pitch Shift vs Varispeed

Calculate the Target Before Processing

Do not stretch by ear when the destination has an exact duration. Write down the original length and target length first. For a clip that must move from 30.000 seconds to 27.500 seconds, the target duration is 27.5 ÷ 30 = 91.67% of the original. Check which value the active dialog requests (new length, percentage or ratio) before entering the number.

For tempo matching, use new duration = old duration × old BPM ÷ new BPM. An eight-second phrase recorded at 120 BPM must become 7.5 seconds to fit the same musical span at 128 BPM. That is a 93.75% duration target. This calculation avoids repeated preview-and-undo passes and gives you a result that lands on the intended edit point.

Leave a clean source untouched. If the clip needs trimming, do that non-destructively in a copy or prepare the boundaries with the Sound Forge cut and trim workflow. Every new algorithm comparison should start from the same original, not from a file that has already been stretched once.

Change Duration Without Changing Pitch

1. Duplicate the file or save a working copy.
2. Select only the passage that must change. With no selection, Sound Forge processes the entire file.
3. Choose Process → Time → Time Stretch or Process → Time → élastique Timestretch.
4. Enter the calculated target length or ratio.
5. Choose the available mode that best matches speech, music, or the source material.
6. Preview the hardest transient and the most exposed sustained sound, not just the quiet opening.
7. Apply once, then verify the new duration, peaks, and both edit boundaries.

The current Sound Forge Pro 2026 Time Stretch help documents both commands under the Process → Time submenu and confirms that no selection means the entire file is processed. It does not promise that either method is transparent on every source.

Speed Up or Slow Down Audio Without Changing Pitch

To speed audio up without raising the voice or musical key, enter a shorter target duration and keep pitch unchanged. To slow audio down without lowering pitch, enter a longer duration and keep pitch unchanged. For narration, remove dead air and tighten pauses before stretching every syllable. For music, calculate the target from BPM and verify the bar line after processing.

If the installed élastique dialog offers source modes, use them as starting points rather than promises: a speech or soloist mode fits one clean voice or pitched source, while a general or polyphonic mode fits mixed material. A reverberant vocal is not clean monophonic speech, and a full mix is not a solo source. The online Sound Forge help sends you to the ? button in the active FX dialog for the controls present in that build.

Which Source Exposes Which Problem?

Speech reveals doubled breaths, metallic consonants, and unstable vowel tone. Drums reveal softened attacks, pre-echo, and flams. Bass reveals a wandering note center or a blurred start. Sustained pads and ambience reveal chorusing, pulsing, and repeating texture. A setting that survives a drum loop may still fail badly on a solo voice.

There is no universal “best” stretcher. In an audio-engineering discussion comparing pitch-shift and time-stretch algorithms, engineers reach for different tools on percussion, bass, speech, solo instruments and full mixes. That thread is useful for choosing test material, not for declaring a Sound Forge winner without a controlled comparison.

Choose the Method by Material

Start with the smallest change that solves the timing problem. A short voice-over correction often works better when you tighten natural pauses first and stretch only the remaining difference. A loop may need its first transient aligned before any algorithm is blamed. A long music master may sound more natural if the timing problem is repaired in the multitrack session rather than forced into one stereo file.

• Dialogue: preserve consonants and breaths; test the quietest exposed sentence.
• Drums: protect the leading edge; compare kick and snare attacks at matched level.
• Full mixes: inspect cymbals, reverb tails, and stereo image movement.
• Ambience: listen for a repeating cycle that was not present in the source.
• Loops: verify bar length and the seam after the loop repeats, not only the first play.

If timing relies on exact boundaries, add markers before processing and recheck them afterward. The markers and regions guide covers named reference points and region boundaries that make before/after timing easier to verify.

Protect Partial-Selection Boundaries

Processing the middle of a file creates two joins: untouched audio into the stretched selection, then the processed selection back into untouched audio. Even when the algorithm sounds clean, those joins can click, change ambience abruptly, or move a breath unnaturally. Place the selection boundary in stable room tone or between musical attacks when possible. Keep handles on both sides so the transition can be repaired without reopening the stretch process.

After rendering, audition from several seconds before the first boundary to several seconds after the second. A click heard only at the join is a boundary problem, not proof that the time-stretch algorithm failed. Repair the boundary with a short fade or crossfade from the original handles. Don’t hide a smeared transient under a long crossfade; move the boundary away from the transient or return to the original and use a better selection.

When the processed selection becomes shorter, everything after it moves earlier in a destructive single-file edit. That may be correct for a finished voice-over, but wrong for material tied to later markers, picture sync, or chapter times. Record the original and target positions before processing. For timing-sensitive work, render the changed section to a copy and replace it only after its start, end, and downstream markers have been checked.

Change Pitch Without Changing Duration

1. Select the note, phrase, or complete file that needs transposition.
2. Open Effects → Pitch → Shift.
3. Enter the change in semitones or cents.
4. Enable the mode that preserves duration when the edit point must not move.
5. Preview the most exposed note and the transition into unprocessed audio.
6. Apply from the untouched source and check peaks, tuning, and timbre.

The current Sound Forge Pro 2026 Pitch help distinguishes Shift from Bend: Shift applies a fixed change, while Bend uses an envelope that moves pitch over time.

Do not confuse pitch shift with normal sample-rate conversion. A proper resample recalculates the samples for a new rate while preserving playback duration and pitch. Sound Forge’s separate Set the sample rate only option changes playback rate without recalculating samples, so pitch and duration change together. The sample-rate guide covers delivery conversion; the linked-rate option is for a known speed error or a deliberate varispeed result.

Semitones, Cents, and Formants

Twelve semitones equal one octave, and 100 cents equal one semitone. Cents are useful for small tuning corrections; semitones are easier for musical transposition. A technically correct +3-semitone shift can still make a voice sound smaller or cartoonish because vocal identity depends on resonances called formants, not only the fundamental pitch.

When a voice must remain natural, compare consonants, vowels and breaths separately. If a global shift fixes one syllable but damages the rest, process a tighter selection or move to a note-aware editor. Formant preservation is not identity preservation: a large move can still change articulation, texture and the apparent speaker.

For a fixed musical transposition, the frequency ratio is 2^(semitones ÷ 12). One octave is 12 semitones and doubles frequency; one semitone is a ratio of about 1.05946. For a measured correction between two frequencies, use cents = 1200 × log₂(target ÷ source). The formula gets the pitch interval right; it does not predict whether the processed voice or instrument will sound natural.

Use Pitch Bend for Motion

Choose Effects → Pitch → Bend when the pitch must rise, fall, dive, or return over time. Sound Forge lets you draw an envelope, set its range in semitones, create up to 16 points, and choose curve types between points. The waveform can be shown in the graph, although the current help notes that it is unavailable when the selection exceeds 300,000 samples.

The Preserve original duration option keeps the edit length fixed. Boris FX says it works best for small corrections up to about ±2 semitones. That is useful guidance, not a cliff: difficult speech may reveal artifacts earlier, while a deliberately synthetic sound may tolerate much more.

When Varispeed Is the Correct Answer

Old tape and turntable transfers can contain a linked pitch-and-time error. Correcting only duration leaves the material in the wrong key; correcting only pitch leaves it at the wrong speed. In Sound Forge, open Process → Resample, enter the corrected sample rate and select Set the sample rate only. The current Resample help explicitly warns that this changes playback rate and does not preserve the original pitch.

For a constant speed ratio r, new duration equals old duration ÷ r, while pitch moves by 12 × log₂(r) semitones. Correcting a 33⅓ RPM transfer that should have run at 45 RPM uses a 1.35 speed ratio: duration becomes about 74.07% of the transfer and pitch rises about 5.19 semitones. Use the exact source and intended rates rather than rounding the pitch first.

Confirm that the error is constant before applying one ratio. A machine that drifted during playback needs a changing speed correction, which Sound Forge’s one-time sample-rate setting does not provide. A tape-stop ramp is also a changing-rate effect: Pitch Bend can create that linked result only with Preserve original duration off. If the final timing curve must hit an exact frame or beat, use a tool with explicit speed automation. Keep the original capture, document the applied ratio and postpone normalization until speed and pitch are settled.

Know When Not to Stretch

A large timing mismatch is often an editing problem disguised as a processing problem. Tighten pauses in narration before forcing every syllable through a heavy stretch. Recut a music cue on a bar or phrase boundary before compressing the entire mix. If the source is a multitrack session, repair timing at the track or stem level instead of asking one stereo master to preserve every transient and reverb tail at once.

Set a practical rejection point before listening. If the processed voice no longer sounds like the same speaker, the groove changes, or ambience develops an audible cycle, the correct answer is not another pass. Return to the source and change the edit, target, or tool.

When Melodyne or SpectraLayers Is Better

A global Sound Forge process moves everything in the selection. If only one note, syllable, or source inside a mixture needs correction, Melodyne or SpectraLayers may be more appropriate. Sound Forge supports ARA integration, but the external software must be installed and licensed for the workflow available on that machine.

The current ARA integration documentation gives two details worth following: the VST3 path must be available in Sound Forge’s VST Effects preferences, and Melodyne should be opened through Tools → Edit in Melodyne (ARA) rather than loaded into the ordinary Plug-In Chain. SpectraLayers has a corresponding Tools → Edit in SpectraLayers (ARA) command.

If a plugin does not appear, work through the Sound Forge VST troubleshooting guide before changing the audio or reinstalling unrelated components.

Final Quality Control

1. Match playback level before comparing original and processed files.
2. Play several seconds before and after both boundaries.
3. Check the exact target duration or edit marker.
4. Inspect new peaks; resynthesis can create sample values above the original peak.
5. Listen in mono for unstable phase or image collapse.
6. Compare speech consonants, drum attacks, bass note starts, and reverb tails.
7. Save the processed master once, then perform format conversion from that master.

Do not normalize before deciding whether the process is acceptable. A louder candidate can seem better even when it contains more artifacts, so level-match the comparison first. Once the edit passes, use the normalization guide only if delivery requires a peak or loudness adjustment. For format changes, follow the audio conversion workflow instead of repeatedly resaving the stretched file.

Common Failures and Fixes

• The result lands at the wrong time: recalculate from original and target duration; do not guess the percentage.
• Speech sounds metallic: reduce the amount, try the alternate time-stretch method, and test a tighter selection.
• Drums have a soft double attack: return to the source and prioritize transient preservation.
• The voice is in tune but sounds like a different person: the pitch changed while the formant character did not survive naturally.
• A loop clicks after stretching: check the seam and apply a controlled boundary repair rather than stretching the processed result again.
• ARA opens like a normal plugin: use the Tools-menu ARA command instead of loading the plugin through the ordinary chain.

Time Stretch and Pitch Shift FAQ

Can Sound Forge change tempo without changing pitch?

Yes. Select the audio and use Process → Time → Time Stretch or élastique Timestretch. Enter a shorter duration for a faster tempo or a longer duration for a slower tempo, leave pitch unchanged, and verify the final timing from the original source.

Can Sound Forge speed up audio without a chipmunk voice?

Yes. Shorten the target duration with Time Stretch or élastique Timestretch while keeping pitch unchanged. For narration, remove excess pauses first so the algorithm has less work to do.

Can Sound Forge slow audio without lowering pitch?

Yes. Set a longer target duration and leave pitch unchanged. Preview exposed speech, bass, cymbals and ambience because large slowdowns can reveal metallic, watery or repeating artifacts.

Can Sound Forge change pitch without changing length?

Yes. Use Effects → Pitch → Shift and preserve duration. Use cents for fine tuning and semitones for musical transposition, then check formants, timbre and edit boundaries.

What is the difference between time stretch and varispeed?

Time stretch changes duration while preserving pitch. Varispeed links them: faster playback raises pitch and shortens duration, while slower playback lowers pitch and lengthens it. Sound Forge’s Set the sample rate only option performs a constant linked-rate change.

Why does stretched audio sound metallic?

The algorithm is resynthesizing audio beyond what the source tolerates cleanly. Return to the untouched file, reduce the change, compare the alternate stretcher, and audition exposed consonants or sustained notes.

Should I stretch a file in several small passes?

Not as a default workflow. Reprocessing an already stretched file accumulates damage. Compare settings as separate one-pass renders from the same original and keep the least damaged result.

Does Sound Forge include Melodyne or SpectraLayers?

Do not assume it does. Sound Forge supports ARA workflows, but installation, licensing and edition availability depend on the products installed. Check the current vendor listing for your edition.

Lock the Target Before Processing

Define what must stay fixed, calculate the target before opening the process, render every comparison from the untouched source, and judge the hardest transient or exposed note before processing the full file.

Last fact-checked August 12, 2026 against the current Sound Forge Pro 2026 Time Stretch, Pitch, Resample and ARA help.